Tutorial on how to remove a freewheel from a bicycle wheel.
First remove the skewer from the wheel. Then identify the correct tool to remove the freewheel. Once you have the correct freewheel tool, place it over the axle and slide it into place on the freewheel. Then take the skewer you just removed and place it back onto the hub, tightening it down until there is a little pressure on the freewheel tool to hold it into place on the freewheel body.
Next grab a big wrench and place it on the tool and turn the freewheel tool counterclockwise.