There must be a online help or book you can read, because there are literally hundreds of answers to your question. However at the end of the day, it is what works best for you and your new DP.
Tell him you are not very experienced (on top) and then suggest you both try everything you can, to see which you like.
How do I move once I am up there so to speak.
Easy answer is put years knees either side (of DP) and slide/bounce/grind up and down (like riding a horse). Changing your upper body angle creates different sensations. From leaning forward (maybe kissing) to leaning right back (grab his ankles for support). Also depth of penetration (controlled by you) creates different sensations
You can obviously do all of the above facing away from DP (reverse cowgirl).
Get DP to sit on something like a chair, then straddle him.
Get DP to lie on the edge of the bed then essentially sit on him (you will be sideways on). Your legs will still be on the floor, so you use your legs to slide/bounce/grind up and down.
Cavewomen's favourite. DP lies on his back (flat) you lie on top of him, you back to his front. This is a horizontal rear entry position with the mans hands free to play.
Happy practicing.