Take the crank bolt out ( 8mm allen key or 14mm socket ), thread in crank extractor into crank arm, tighten to remove crank. The old freewheel then needs to be removed from the crank arm, shopuld just be a basic 4-prong acs tool. Clamp the tool into a vice, bolt the crankarm reasonably tightly to the tool. Remove pedal and slide a scaffold bar or similar over the crank arm, turn anti-clockwise to remove from FFW. Once it's shifted a bit, remove bolt and proceed with care.