I really like this girl and I'm not sure what to do?

Alrighty well during high school I was a lil popular and funny but wasnt really the best with the girls and now I have a new opportunity to change that. I moved with my dad this previous summer and have been hanging out with my 17 year old cousin and he totally runs this town I feel like Im a king when Im with him all the girls are like HUNTER!!! and then of course who's this?(meaning me) lol so i kinda feel pretty good and he introduced me to this girl and i was like wow dude shes just perfect i want to get to know her but im so nervous because she doesnt know me at all... I need some help PLEASE!!!