Apply either teflon tape or pipe joint compound on the threads of the nipple. Hand tighten nipple to towel warmer. With an allen wrench inserted into the nipple, hand tighten to secure appropriate fit. Set valve into position and seat copper tubing into the base of the valve. Seat the union nipple into the valve and loosely tighten the union nut.
Hand tighten the compression nut.
Turning the valve body will split the compression ring, making a good seal unlikely. Tighten union connection to valve. Repeat for second valve. Water is ready to be circulated through your Myson towel warmer at this time. Connect towel warmer to hot water system using one of the options shown below.