How to ride my guy on top?

I just started sleeping with a new guy, and he wants me to ride him, and be dominant a few times, but I'm much less experienced than him, and I hadn't been with anyone for about four years. Tips are welcome, please and thank you. I've never rode a guy, and I don't want to look dumb. I'm 26, and he's 20, yes, I know, it's weird him being younger, I fought the idea.