1) Lock it down.
2) Turn it sideways. Use the leveling screws to center the bubble level.
3) Carefully loosen the hanger rod and release slowly the tension to allow
the mass to recenter.
4) Look through the little viewhole next to the rod to make the white lines
line up. This means the mass is centered.
5) Look at the output on a scope. It should be freely moving with a ~1 sec.