The pickup is attached to a plate/bracket that has slotted holes. Loosen the phillips screw (replace them with allen heads when you can) and spin the flywheel so the nubs are at the pickup, use a feeler gauge to set the gap, then tighten down the screws for the pickup.
Spin the flywheel 180 degrees, check the other nub. I've seen a .001 to .002 variance sometimes...no biggie.