I did the exact same thing quite a few years ago when I removed the LSD R200 from a fire damaged R31 turbo coupe; removed the flange from my old R200 with impact socket on air gun, and as Mike has said, tighten to correct torque... then removed stub axles from my old R200, swap left to right and install into LSD diff. You should feel both axles "click" and lock in place when installed. If you look inside where the stub axles go in, you can see one is longer than the other. Its not that complicated to do.
Clutch pack LSD's should have resistance when trying to rotate one wheel in an opposite direction to the other when the rear is jacked up off the ground.