wpmem_default_text

$defaults = array(
    
    // Login form.
    'login_heading'        => __( 'Existing Users Log In', 'wp-members' ),
    'login_username'       => __( 'Username or Email', 'wp-members' ),
    'login_password'       => __( 'Password', 'wp-members' ),
    'login_button'         => __( 'Log In', 'wp-members' ),
    'remember_me'          => __( 'Remember Me', 'wp-members' ),
    'forgot_link_before'   => __( 'Forgot password?', 'wp-members' ) . ' ',
    'forgot_link'          => __( 'Click here to reset', 'wp-members' ),
    'register_link_before' => __( 'New User?', 'wp-members' ) . ' ',
    'register_link'        => __( 'Click here to register', 'wp-members' ),
    
    // Password change form.
    'pwdchg_heading'       => __( 'Change Password', 'wp-members' ),
    'pwdchg_password1'     => __( 'New password', 'wp-members' ),
    'pwdchg_password2'     => __( 'Confirm new password', 'wp-members' ),
    'pwdchg_button'        => __( 'Update Password', 'wp-members' ),
    
    // Password reset form.
    'pwdreset_heading'     => __( 'Reset Forgotten Password', 'wp-members' ),
    'pwdreset_username'    => __( 'Username', 'wp-members' ),
    'pwdreset_email'       => __( 'Email', 'wp-members' ),
    'pwdreset_button'      => __( 'Reset Password' ),
    'username_link_before' => __( 'Forgot username?', 'wp-members' ) . ' ',
    'username_link'        => __( 'Click here', 'wp-members' ),
    
    // Retrieve username form.
    'username_heading'     => __( 'Retrieve username', 'wp-members' ),
    'username_email'       => __( 'Email Address', 'wp-members' ),
    'username_button'      => __( 'Retrieve username', 'wp-members' ),
    
    // Register form.
    'register_heading'     => __( 'New User Registration', 'wp-members' ),
    'register_username'    => __( 'Choose a Username', 'wp-members' ),
    'register_rscaptcha'   => __( 'Input the code:', 'wp-members' ),
    'register_tos'         => __( 'Please indicate that you agree to the %s Terms of Service %s', 'wp-members' ), // @note: if default changes, default check after wpmem_tos_link_txt must change.
    'register_clear'       => __( 'Reset Form', 'wp-members' ),
    'register_submit'      => __( 'Register', 'wp-members' ),
    'register_req_mark'    => '<span class="req">*</span>',
    'register_required'    => '<span class="req">*</span>' . __( 'Required field', 'wp-members' ),
    
    // User profile update form.
    'profile_heading'      => __( 'Edit Your Information', 'wp-members' ),
    'profile_username'     => __( 'Username', 'wp-members' ),
    'profile_submit'       => __( 'Update Profile', 'wp-members' ),
    'profile_upload'       => __( 'Update this file', 'wp-members' ),
    
    // Error messages and dialogs.
    'login_failed_heading' => __( 'Login Failed!', 'wp-members' ),
    'login_failed'         => __( 'You entered an invalid username or password.', 'wp-members' ),
    'login_failed_link'    => __( 'Click here to continue.', 'wp-members' ),
    'pwdchangempty'        => __( 'Password fields cannot be empty', 'wp-members' ),
    'usernamefailed'       => __( 'Sorry, that email address was not found.', 'wp-members' ),
    'usernamesuccess'      => __( 'An email was sent to %s with your username.', 'wp-members' ),
    'reg_empty_field'      => __( 'Sorry, %s is a required field.', 'wp-members' ),
    'reg_valid_email'      => __( 'You must enter a valid email address.', 'wp-members' ),
    'reg_non_alphanumeric' => __( 'The username cannot include non-alphanumeric characters.', 'wp-members' ),
    'reg_empty_username'   => __( 'Sorry, username is a required field', 'wp-members' ),
    'reg_password_match'   => __( 'Passwords did not match.', 'wp-members' ),
    'reg_email_match'      => __( 'Emails did not match.', 'wp-members' ),
    'reg_empty_captcha'    => __( 'You must complete the CAPTCHA form.', 'wp-members' ),
    'reg_invalid_captcha'  => __( 'CAPTCHA was not valid.', 'wp-members' ),
    'reg_generic'          => __( 'There was an error processing the form.', 'wp-members' ),
    'reg_captcha_err'      => __( 'There was an error with the CAPTCHA form.', 'wp-members' ),
    'reg_file_type'        => __( 'Sorry, you can only upload the following file types for the %s field: %s.', 'wp-members' ),
    
    // Links.
    'profile_edit'         => __( 'Edit My Information', 'wp-members' ),
    'profile_password'     => __( 'Change Password', 'wp-members' ),
    'register_status'      => __( 'You are logged in as %s', 'wp-members' ),
    'register_logout'      => __( 'Log out', 'wp-members' ),
    'register_continue'    => ( isset( $wpmem->user_pages['profile'] ) && '' != $wpmem->user_pages['profile'] ) ? __( 'Edit profile', 'wp-members' ) : __( 'Begin using the site.', 'wp-members' ),
    'login_welcome'        => __( 'You are logged in as %s', 'wp-members' ),
    'login_logout'         => __( 'Click to log out', 'wp-members' ),
    'status_welcome'       => __( 'You are logged in as %s', 'wp-members' ),
    'status_logout'        => __( 'click to log out', 'wp-members' ),
    'menu_logout'          => __( 'Log Out', 'wp-members' ),
    
    // Widget.
    'widget_status'         => __( 'You are logged in as %s', 'wp-members' ),
    'widget_logout'         => __( 'click here to log out', 'wp-members' ),
    'widget_login_failed'   => __( 'Login Failed!<br />You entered an invalid username or password.', 'wp-members' ),
    'widget_login_failed_new' => __( 'Invalid username or password.', 'wp-members' ), // @todo New string replacement. Replace widget_login_failed when translated.
    'widget_not_logged_in'  => '',
    'widget_login_username' => __( 'Username or Email', 'wp-members' ),
    'widget_login_password' => __( 'Password', 'wp-members' ),
    'widget_login_button'   => __( 'log in', 'wp-members' ),
    'widget_login_forgot'   => __( 'Forgot?', 'wp-members' ),
    'widget_login_register' => __( 'Register', 'wp-members' ),
    
    // Default Dialogs.
    'restricted_msg'       => __( "This content is restricted to site members.  If you are an existing user, please log in.  New users may register below.", 'wp-members' ),
    'success'              => __( "Congratulations! Your registration was successful.<br /><br />You may now log in using the password that was emailed to you.", 'wp-members' ),
    
    // @todo Under consideration for removal from the Dialogs tab.
    'user'                 => __( "Sorry, that username is taken, please try another.", 'wp-members' ),
    'email'                => __( "Sorry, that email address already has an account.<br />Please try another.", 'wp-members' ),
    'editsuccess'          => __( "Your information was updated!", 'wp-members' ),
    
    // @todo These are defaults and are under consideration for removal from the dialogs tab, possibly as we change the password reset to a link based process.
    'pwdchangerr'          => __( "Passwords did not match.<br /><br />Please try again.", 'wp-members' ),
    'pwdchangesuccess'     => __( "Password successfully changed!", 'wp-members' ),
    'pwdreseterr'          => __( "Either the username or email address do not exist in our records.", 'wp-members' ),
    'pwdresetsuccess'      => __( "Password successfully reset!<br /><br />An email containing a new password has been sent to the email address on file for your account.", 'wp-members' ),
    
    'product_restricted'   => __( 'Sorry, your account does not have access to %s content', 'wp-members' ),

); // End of $defaults array.

add_filter( 'wpmem_default_text', function( $text ) {
    
    // Based on the default values, set an array value
    // for each of the text strings that you need changed.

    $text['login_heading']    = 'Log In to Your Account';
    $text['register_heading'] = 'Register New Account';

    return $text;
});