There is an alighment bar that you use to align it. You align it from left and right and also center to center. It is easy to do and adjust. You also check belt deflection when you are done getting the clutches aligned. Many companies like High Performance Engineering sell the alignment bar.
Without a bar, just loosen the secondary bolt up and run it slowly on a stand. Stop it and see where your secondary is riding, that should be in a true line. Put the right amount of washers in so that it can float in and out about 1/8" Make sure the engine is sitting against the stop.
