@kent0111,
If her boyfriend looks like he could whip your butt, then you might not want to try too hard to get her to like you. But as previously noted, you could just tell her you'd like to friend her on FB and if she says ok, then send a friend request.
If, however, you think you could physically handle her boyfriend, just walk up to the two of them, look her in the eye and declare your intention of stealing her affections away from the poor specimen of a man that she has been dating.
Of course, if you want to REALLY impress her, try option 2 even if you are certain her boyfriend could wipe the floor with your sorry butt.
Good luck.