Make sure he knows you want it, otherwise it makes him unsure and uneasy about if he should push further. A lot of guys like hearing, "I want you so bad", 1) because it's an obvious indicator 2) duhhh it's hot! Alssoooo, [ and this is just basic stuff], obviously make sure you're wet, or it's going to hurt like hell. If you're still worried about the pain, try going on top, then you can ease yourself in [ bahaha].
Don't go into it too seriously. Instead of trying to make it this incredible romantic moment, try to just have fun.