How Should I Approach My First Relationship With A Butch ?

I'm bi and really prefer women. Every woman I've ever been in a relationship has been in the middle of the spectrum. I like women because they're women! But I'm trying to be more open minded. I have no idea how to approach things though.... since I've been with guys too I almost feel as if I'm at a disadvantage. Can you help me? Any advise? I'm SOOOO nervous!