I would pinch it back now.

Not sure what how to pinch them back. What exactly is that.

Another question. I planted the clematis against one of the 3 legs of the Teepee, should I have planted it in between 2 of the legs? Thought that I should ask now as if I need to replant it I can today.

I don't think you need to replant, you can put it anywhere around or even in the tee pee that you want. Pinching is pruning, they are so soft at that age you can often do it with your hands instead of clippers. I would take those vines down by half.