That all depends. Where are you with the girl? If your in front of a cluster of people, then, I wouldn't finger her there. Doing that would most likely make her feel very uncomfortable. Try and isolate her into a room of some sort where its just you two, or depending on how many people your getting with
. If that is not possible, then try and go to a place with as little as possible people. You'll probably enjoy it more, and so will she. Its not hard to finger a girl. As your making out, just start rubbing her, thighs, waist, whatever, and then gradually work your way inward. Relax, enjoy it, and try to tease her.