best thing to do would be finding a buddy that knows pumping and learn visually. Or watch tons of youtube videos and get the idea stuck in your mind. Are you stiff when you pump? Be loose and enjoy the ride. Gather a speed of about 5-6 mph before you start. Its hard to pump at slower speeds for a beginner. I can't really explain the motion of the legs and body to well so read
www.pavedwave.org about that. Starting with huge carves might help you get hte feel of pumping, you might fall off but dont give up, you'll learn if you keep practicing.