Now that you have the O-ring completely on, you are ready to reconnect the neck back to the base of the faucet.

Screw the neck back on the base of the faucet and tighten it with your bare hands.

Make sure it is tight but not too compressed. So use your bare hands. You want the O-ring to be able to seal off the faucet base as to not cause any leakage but not so much so that you are unable to unscrew them again.

Remember to turn your water back on by turning the water supply valves under the sink!