BuddyPress.org

Sorry, what I meant to say is if you already know how to create custom write screens, etc. for WP, then it’s the exact same thing for a site running BP.

If you don’t know how to create a non-backend custom write page then unfortunately, this isn’t really the place to ask as it’s not really a BP issue. However, you could look at the WP TDO miniform plugin as I believe it can do this sort of stuff.