-Put the freewheel tool on the freewheel, and hold it in place with the wheel nut.
-Put the TOOL in a vice and turn the wheel, like you were driving a bus.
This is THE best way to remove a freewheel. Works even better if you have a nice fat tyre on there for extra leverage.
(Note: make sure that once the freewheel is "cracked" and has started moving, you stop and take of the wheelnut. It wont come off very far with it on there)