How do I ask my friend to the dance!!

Ok I'm homeschooled and I go to a tutorial. So i was involved in some drama because I was trying to help and save friendships. (Love triangle, two guys & 1 girl) so the girl is going with the other guy (C) and the other guy (D) wanted to dance with somebody. When he found out I was going to the dance he asked if i would just slow dance with him at least once. Now we mess with each so I want to make a poster and ask him during lunch at our tutorial if he would save a dance for me but I don't know how😅 please I need advice