what should I do with this girl!

so, I have a crush on this girl! an I finally got to talk to her on facebook, she’s pretty nice and everything. I wanted to get to know her long time ago and now it’s the time to get to know her. I want to ask her but I can’t really do from the first time I go with her. I mean what should I tell her? should I tell her I liked for while and I wanted to get to know but I didn’t have the chance or should I just start fresh with her and not tell her about the past? I want to do the right thing with her but how should I start? can I get a real help right here please. People said she would be down if I talked to her and made her like me. But I want to spite my game right and I want put the good cards in that game! please help! thanks :)