The key is to be patient and understanding. He's new to this, and DEFINITELY new to talking about this out loud with another human being. A sense of humor and a lot of reassurance will go a long way. Frame your requests as, well, requests, clearly explained, and not as a critique. It may feel weird to be so matter-of-fact about something that we often want to feel spontaneous, but until he knows what you like (and what he himself likes), it's the only way.

Make sure you ask a lot of questions about what he wants, as well. Don't scoff or put down "vanilla" stuff if he mentions it. Ask him how he feels about stuff, and when you DO try new things that you like, make sure you tell him, give him positive feedback.

Honestly, it sounds like you have a very loving and healthy approach here, so I doubt you're going to laugh at him or something, but making him feel comfortable talking about it all, and making him feel listened to, will really help.

ETA: I realized this is all very focused on making him comfortable, and not advocating for what you want in the bedroom. There's nothing wrong with you wanting more variety in your sex life. I just think that this way will be better for ensuring that it's a fun and intimate experience for you both, and that he'll gain confidence and comfort with you along the way, which will help make it all more organic.