Once you learn how to turn left and right, skiing on a run will be much more enjoyable. The trick is just to keep your skis in a V-shape and aim your chest toward where you want to go. Your skis will naturally turn toward the direction of your chest. Practice turns with this method and learn how it feels.
Aim your chest to the left
Begin with making one turn and stopping each time. Keep your skis in a V-shape and ski straight. Once you turn your chest to the left, you will move in that direction. Keep yourself balanced so that your body won't lean back every time you turn.
Aim your chest to the right
Likewise, aim your chest to the right to do the right turn. Keep your skis in a V-shape and move straight forward, then aim your chest to the right to do the right turn.
You will not turn if your body is twisted
If you are tightening your muscles and your body is twisted, you won't have much control of your skis. Be sure to keep your weight right between your legs down the centerline of your body, regardless of whether you are skiing in a straight line or turning.