You need a lockring removal tool and a chainwhip to remove a cassette. Clamp the tool in place with the qr skewer and be sure you are turning the removal tool the correct way, it has standard right-hand threads. Wrap the chain whip around one of the cogs and hold the cassette stationary while you thurn the removal tool. You can turn the wheel over and clamp the remover tool in a bench vise instead of using a wrench if you have one available.