[xx22xx]

Taking into consideration that you've never fingered a girl before, then you just might have been at a bad angle. If it's possible, take off her pants, and her underwear if she's comfortable with that too. Start with one finger, and be gentle. Try to get into a position where you have the ability to move your entire arm, with your finger, if you get what I'm saying. That was, she's most likely laying on her back, and it's kind of easy access. As for fingering techniques/more detail on how to do it, check the pleasing her section. I know I've made a few posts there.