How to approach this girl?

my friend dated this one girl who we went to high school with. shes cool and really pretty. anyway they broke up and she dated another guy and that ended. i saw her profile on ok cupid(dating site) and told my friend. he said i should ask her out on a date but in all honestly not sure how i would approach the subject with her. I know who she is. I have hung out with her through mutual friends multiple times. We have always gotten along well

what would be a good way to talk to her on there and approach the subject?