I've been trying to turn but every time i try he goes straight through the curve any help?

The line rider engine is pretty confucing if your just starting out. Depending on the direction that you draw your line, the solid side of the line(the one your character won't go through) will either be on the top or bottom.

If you want to turn, say, slightly upward, you need to drag the line towards the right side of the screen, then slightly upward. If you drag the line from right to left, your character will pass right through the line. When you drag from right to left, the solid side is facing down, and if you drag left to right, the solid side will be facing upward.