Hi @simonmnt,
you should create a correct child-theme to get BP templates customization to work.
First, you need to declare the child via /your-child/style.css with the correct header information.
Eg. for a twenty fourteen child
/*
Theme Name: Fourteen-Child
Description: My child theme for Twenty Fourteen
Version: 1.0
Author: simon
Template: twentyfourteen
*/
@import url("../twentyfourteen/style.css");
Once done, you can select this child as site theme.
Now you can add a /buddypress/ folder to /your-child/
Inside this folder, you copy any file you need to modify from /bp-legacy/buddypress/
You copy only the file(not the whole /bp-legacy/buddypress/ folder) you want to change, by respecting eventually the original path. Eg
.
/your-child/buddypress/members/single/profile/profile-loop.php
If you need custom functions for the theme, you add a file called functions.php inside /your-child/functions.php
If you need custom functions for BuddyPress (like most of the snippets you can find on this forum), you add them to wp-content/plugins/bp-custom.php
