So there you are, standing at the bottom of the ramp. Hop on your skateboard, and give yourself a push aimed right up one of the walls of the vert ramp. Bend your knees. As you start to feel yourself loosing speed up the side of the ramp, you want to push out with your knees and focus on pushing the board higher up the ramp.
Once you get to the top of your push, when the skateboard starts to roll backwards back down the ramp, you want to put your weight back onto the board, and push down hard. Imagine the ramp is soft, and you are actually forcing your wheels through the ramp. This will take some practice, but you'll get the hang of it.
You’ll have gained a lot of speed as you come off the side towards the other side of the ramp. Do the same thing here, back and forth, going higher. Practice it a lot, and don't stress about not learning fast enough. Soon you will get the feel for how pumping on a vert ramp works. Keep practicing!
Once you feel more comfortable, you can try pivoting on the ramp, at the top of your push. Some skaters find it easier to pivot, instead of rolling back fakie. Either way is fine - you will want to practice them both eventualy. Whichever works best for you, relax, and go for it!