Cowgirl position?

I honestly don't know how to ride him. How do I position my legs? Am I using my legs to push myself up and down? Like I've tried once. My boyfriend tried to tell me what to do, and I completely failed. I just got off and told him to go on top. I honestly...

don't get it.

Maybe its because you are still so young...

well see depends which you are doing...like you could put your hands beside him and use them to grind against him or to has s*x...or just be on your knee's and go up and down to F*ck him(this way doesn't have much grinding I assume)

There are many possibilities and you have to find out all of them. But the simplest is that if you are kneeling when sitting in the d*ck, and yes, you may elevates your body mainly by your legs. You can practice it also alone. But when the dű*ck is in you, then you have bend forward a little, and you may lean on your arms/hands.
http://www.illustrated-lovemaking-positions.com/images/cowgirl.jpg

You could try supporting yourself by your hands and sit on his lip while he's in you, and then roll your hips around and grind down against him. Or, if you want to really move, kind of lean forward and then sit backward. Like you're sitting and standing from a chair.