One of the basic elements of WordPress best practices is to use a Child Theme. This allows you to make customizations to your theme without worrying about losing those changes when the theme author releases an update. It’s simple to set up and should be a standard practice when setting up a new site.
This example will create a child theme of the WordPress default theme Twenty Seventeen. The purpose of this exercise is to help you get a custom child theme so you can store custom functions for customizing WP-Members. It is not intended to be a complete process of developing child themes and custom template files. There are plenty of those resources available on the Internet, starting with the WordPress Codex.