Its easy to sight your bow in. You follow the arrow with your sights.

I.E. Your arrows are hitting high of the bullseye, move your pin up. Hitting low, move the pin down. Right, move it to the right. Get the idea?

I would say get your new arrows and shoot at 20 yards. If your arrows are hitting low then move your whole sight down. This should keep your 30 and 40 yard pin fairly close so you don't shoot a tree.