Put on gloves. Wrap a chain around the post 24 inches up from the ground. Loop the chain around several times leaving some slack in one of the loops.
Stand the high-lift jack beside the post. The high-lift jack resembles an old-fashioned pump. It has a 90-degree shelf or lip on one side, with the pump-handle on the opposite side. Hook the lip under the loosened or slack loop in the chain.
Pull the lip and chain up together until the lip clicks and removes slack from the chain.
Pump the handle of the jack up and down slowly. As the chain tightens it binds tight around the post. Continue pumping the handle.
Release the tension on the chain by flipping a lever located under the lip, if the post doesn't lift out of the ground before the lip reaches the top of the jack. Lower the lip by pumping the handle until the lip is about 24 inches off the ground.
Slide the chain back down and hook one of the loops around the lip. If the chain is stuck, jiggle it slightly, and it will loosen and drop. Hook the chain on the lip, remove the slack from the chain and flip the lever to lock it in place. Pump the handle until the post lifts out of the ground.