BuddyPress.org

Please this is my first experience with WordPress and buddypress. I have installed wordpress Mu/buddypress successfully, I want to have a site where the main page will be used as an introduction to my social networking site, as well as the platform for login, and the second page to be the main social networking page… i have installed some customed made theme for the purpose of the Social.n/w.. but the whole thing is confusing me. PLEASE… i will be grateful if any one can give me step by step hint on how to go about this…….

….placing one theme as main page in subdomain and the other in main domain is…? Please Help…