Hmm kinda awkward, please help!?

My boyfriend and I are both seniors in high school, and we've been together about 4 months. Sooo he recently fingered me and I want to return the favor by giving him a hand job, but there are a few problems: first, I've never done that before so I don't really know how to initiate it or what to do (I mean it seems pretty straightforward...but still), and second, he's almost a foot taller than me so when we're making out I can't even really reach that area. Sorry this is so blunt, but I need advice! Thanks :)