"...what to do with your guitar once you've tuned it like that"? You mean, besides playing around with it to see what sounds good to you, like you do when you're in standard tuning?

Well, there are books and booklets with chord charts for various alternate tunings; check your local music store or bookstore, or search the music-book sites and order a reference book. If you have a friend who plays in alternate tunings, ask him/her to show you some stuff or point you toward some resources. If you see a performer playing in alternate tunings, watch the fingers for chord patterns, and bend his/her ear after the show to learn more.

Basically, do the same stuff you did when you learned how to play in standard tuning!