It means you've done/experienced something before, or have gone through something before. For example, if you were to tell me "Hey Sage, let's go whitewater rafting this weekend, it sounds exciting!" I'd reply with "Been there, done that." (That's if I had actually done it before). Sometimes, you can even say "Been there, done that, bought the T-shirt", just to really emphasize that you have gone through it before (because, well, when tourists visit a place they usually buy a T-shirt with the name of the place). =D

means having already experienced something before in the past and don't feel the need to experience it again

"been there, done that" = I have been there and I have done that. It just means I've gone through that experience already.

Sage is right. For example if anyone said to me, " Wouldn't you just love to have another child?" I would reply, " Been there, done that". It implies that I have no wish to have anymore children as I have already had them.