just ask her. my metal tech teacher is one of the ugliest people i've ever seen, but he went on dates with mad hot girls through high school and college, and his wife is a real banger too. his advice to me was as follows:
dress like a halfway decent person, take a shower, brush your teeth, and just ask her out. know what the worst thing she can say is? "why the fuck would i ever go out with someone like you?" which really isn't that bad. there's like six billion people out there man, chances are high that someone you find attractive will find you attractive as well.
oh and be confidant. bitches love confidence.