Crushing on a Girl in my Class

So I am a 23 year old male. I have a class with a 18 year old freshman girl. She is absolutely gorgeous and pretty cool it seems like, therefore I have a crush on her. I've never been that great talking to women which is one of my downfalls, however since we have had class together for the last 3-4 weeks we have talked in class and now are "friends" on Twitter and Facebook and talk on there from time to time about class and just life in general, nothing too serious.

My question is how do I get things to progress or let her know im interested. I dont think she really knows I think she is "hot" or that I think shes really cool to talk to and I wouldn't mind hanging out/dating her.

As I said I'm not great with the opposite sex so I need to know how I would go about letting her know im interested (in a subtle manner) and how to get things to progress.

Any help would be great, Thanks in advance.