Stick in an axleshaft into the axle and turn it. It should rotate the pinion gears into place. You need make sure that both gears are in the same (correct) position. Use grease to hold the thrust washers onto the pinions. May need a cheater bar on the axle as well a friend. It shouldn't be too difficult to turn since the preload spring isn't installed.
If you have a choice in clutch material, choose metal. It lasts longer. Carbon fiber is the next best. After that is semi-metallic.
FWIW, our plant builds several million of these a year for another automaker.