Your best solution would be to try and find out his feelings on gays, not directly however probably just in casual talk.
If he responds negatively, there's still a chance he's gay and just trying to cover it up. If this happens then sadly you can't make a move (obviously) and is best just to forget about him
However if he is ok with gay people then slowly drop hints that you like him. Prepare for a backfire in case he's actually not gay/doesn't like you despite being comfortable with gay people, in which you should stop dropping hints.
Usually the dating game doesn't properly happen for gay people until you turn 18 or go to college/university. Info I gathered from friends in uni.