Pass the 12" long, 1" threaded rods through p24 then through the tubes ], through p23 and thread them through the nuts welded to the far side of P4.

Attach the 4 further nuts to clamp the motor to the tubes, and the tubes against p23, in a sandwich

Tighten the 2 screws in the collars of both bearings to the shaft (should be separated by 120 degrees).