Setting Up Member Payment Page

Hi there! I'm almost ready to launch my site re-design with the new WPMU Dev features. I have a simple, single Member option and have the positive and negative rules set. I also have buddypress installed, and that will be part of their paid membership.

My question in the heck do I set up the page where they PAY, then are redirected to the forums, and other members only content?

Thank you so much!