On the left side (non-drive side) of the bike, place the notch of the lock ring wrench into one of the divots on the lock ring.

Ensuring that the curve of the wrench is pressed against the lock ring, turn the lock ring counterclockwise.

It's easy for this tool to slip off while trying to apply torque to the lock ring, especially if the lock ring is very tight. Try to apply all of the force in the same plane as the lock ring to avoid slippage.