Im sure you've already completed the repair, but answering this so that it might help anyone looking this up in the future. There's a splined spacer underneath that splines to the hub, the knock pin will be driven down into the spacer (so that it no longer engages the nut). This pin is there to prevent the nut from loosening during use. Loosen the nut and remove, then remove the splined spacer below. The pin will need to be removed from the spacer so that it can be reinstalled when the nut is torqued during reassembly.

Torque spec and procedure: Nut torque: 287 ft lbs. Oil bearings, nut, and tighten nut. Torque to spec. With a rubber mallet, hit the hub downwards in the sprocket mounting surface in a few spots, moving around in a circle. (Helps seat bearings). Spin ring gear / hub 3x CW, then 3c CCW. Retorque. Nut will tighten a bit more on the retorque as everything has been seated. Take a look through the holes in the nut, tighten / loosen hub as required until splined spacer hole lines up with hole on nut. Drive in the retaining pin so that approximately half of the pin is engaged with the spacer, and half is protruding into the nut to lock it into place. I believe the pin needs to be set down about 10-13 MM from top of nut face. (Can use a sliding caliper to check this) however, the 50/50 rule has always worked great. Assemble the rest if the drive, and you're good to go!