You will need to turn the machine off and allow it to fully cool down before attempting this procedure.
1. Remove the steam knob itself, and then remove the outer piece of the steam valve, pointed out here. Use a towel around the steam valve in order to prevent scratching from the adjustable wrench.
2. Swap the two components, pointed out here. For the joystick you will need to transfer over the washer to the new joystick piece, making sure that the curved inside edge of the washer goes over the half ball side of the joystick.
3. Hold the new joystick piece in place fully seated inside the outer piece of the valve and thread it on to the steam arm with your fingers. Tighten it fully with the towel and adjustable wrench, then reinstall the knob on the end of the joystick.