How do I modify X and Y on my BuddyPress pages?

Most BuddyPress page templates can be modified by adding the directory structure and file within your theme folder to override the default styling as explained here:

However beyond this since BuddyPress is a third party plugin and is not part of the theme you should contact BuddyPress support at where they will be able to help you with modifying BuddyPresss templates.

While the theme completely supports BuddyPress, and even has customized BuddyPress elements, support does not cover customisations (click here for the support policy), this both includes customising the theme and third party plugins.