BuddyPress.org

Generally it would be placed in a functions.php file that lives in a child theme – are you running a child theme? if not I suppose it can be run in bp-custom.php file that lives in the plugin folder but haven’t tested whether that does work. You can place it in the default themes functions.php file but the problem there is that when you upgrade BP you will lose any mods made to this file and any others in the default theme which is why it’s best to run a child theme if planning on making a few mods.