BuddyPress.org

ok so im on the newest wordpress and buddypress.
ive had a look through the following posts and pages:

https://buddypress.org/support/topic/adding-new-order-by-on-members-loop/

https://buddypress.org/support/topic/creating-a-new-order-by-filter-in-groups-loop-with-custom-sql/

Add custom filters to loops and enjoy them within your plugin

Im trying to make ‘Order By’ sections that find users who have ticked a specific profile field in their profile. The first thing im confused about is am i editing the..
/bp-templates/bp-legacy/buddypress/members/index.php OR
/bp-templates/bp-legacy/buddypress/members-loop.php ?
i thought it was member-loop but that last help page suggests index?

Im just not succeeding lol, could you help me please?