How to use it? load your figure, turn on Auto Balance, start posing. You should not normally need to move the CenterOfMass prop. Moving the CenterOfMass prop changes where Poser thinks the center of mass is. For example, supose your figure is carrying a heave weight in its left hand, Poser does not know that the thing in the left hand is heavy. You could shift the CenterOfMass prop to the left to make the balance more realistic.

@ FrankT,  I never use it  either!