How to ask this guy to sadies?

ok so im a freshman and i really wanna ask this guy to sadies but i dont really know how. so i go to an all girls school and we have like a brother school and hes from there. i cant just like ask him easily because i dont see him often. im not sure how i just ask because i dont reallly wanna do it like online. but idk. and he has a twin brother who im pretty sure likes me. so idk what to do? help. puhleez :] k.thanks.bye