When I go snowboarding, I can only go down with my body facing the bottom of the mountain?

If you turn your body your board will follow. When I learned the instructors had us on easy runs with our arms out a little bit and pointing at a spot where we wanted to go. When you move your arm your body and then board will follow it around through the turn. When your body is approaching the fall line (where your board is pointed straight down the hill) you want to stand on the balls of your feet and keep even pressure so that the edges don't bite the snow and abort your turn. Once you've entered the fall line then start to engage your edges to complete the turn. This is a pretty common problem and a few hours on some green runs should work it out! It's never a bad idea to sign up for a lesson and brush up on some basics though :)

so your sliding down on your heels...turn your right upper body up the mountain at the same time your gonna turn your back foot. you will feel the board shifting from perpindicular to parrallel. your board straightens out and you might feel like your goin really fast but dont be scared cause the faster you turn your upper body and back foot the better. when you end up goin straight keep 90 % pressure on your back foot and 10 on your front and then when you follow through on that turn and your body is facing up the mountain...keep equal pressure on both feet as well as your toes. then back to heels and then back to toes...which is carving...

Your board usually turns to where your body and shoulders are turned. So make sure your shoulders stay parallel with your board, and instead, turn only your head to look forward. It will probably help a lot if you increased the angles on your stance.

You are having problems turning your board down the fall line because you are not putting enough pressure on your front leg. When you put equal pressure on both feet or lean back just after starting a turn down the hill, your board will naturally turn back across the hill. Use more pressure on the downhill side of the front foot to release the front of the edge and the board will swing faster toward the fall line. You MUST wait for the board to cross the fall line (straight down the hill) before you transition your weight to the other edge (or you will catch the downhill edge - ouch). Then use equal pressure on both feet on the new uphill edge to get the board to move back across the hill - this is a complete turn. Good Luck

Grow a pair of Testicles.