I feel rather stupid asking this question, because I suspect the answer is right in front of my nose.  However, I can't seem to find it in the game or anywhere online.

My question is this...if I want to use a potion I have brewed on a slave, how do I do that?

Any help would be greatly appreciated.

Goto character window, select gear, look for the potion, at the potion's buttons, press the right most button.