I have been talking to a girl for about a year now, and i'm pretty sure she likes me. But I don't know how to ask her out. Can Someone help.

Maybe it's better to just ask her out. Just calm down and believe it will work out. I think that it's the best way to do this.
Good luck :)

Well if you see her regularly face to face, take her out. For example to the city and walk around..buy her dessert and just chat. Once you're both comfortable, slowly build up to the question. She seems like the shy type so don't blurt out the question out of the blue and certainly don't do it in front of people.
Like Erin said before, calm yourself first and ask. Either way, just be a gentleman no matter the outcome.

Good luck ^^