Take the metal bar off the two magnets if you havn't done that. Now put your fletching into the clamp and place the clamp onto the magnets. Your shaft should be in the jig prior to all this of course. Then loosen the two allen screws and move the dials so that the fletching fits the shaft perfectly and retighten. You can offset the fletching to get a more aggressive spin to the arrow, but I think the most important thing is to make sure the fletching contacts the shaft perfectly.