I would do as Rachel says, have some friendly chat with her then ask her for a drink. I think if she added you to Facebook she must be interested, or at least want to get to know you better, because you dont swap numbers, or try and stay in contact with a fella you've met in a club just coz you fancy having a new pal. Well at least I wouldnt.
My boyfriend and I met in a club (on an efest night out actually ) and we were texting lots after the night we met, and although it was maybe a week before he actually asked to meet up again, we both knew it was headed that way, as why would we have been bothering to text a stranger otherwise.
Good Luck! I was convinced I was shit at the whole dating thing too, but it's been so so easy with my boyfriend, that I now just realise none of those other guys were right for me! (cheese)