The adapter that mounts to the lens port comes with two plastic components that together act as a knob to thread the adapter to the lens port. The adapter that attaches to your wide angle wet lens is attached by removing the screws from the back of the lens-as indicated in the picture in my earlier post-remove the ring that the screws were securing, then install the adapter. Make sure you install on the correct direction to attach to the lens port adapter.
I also purchased a mount for the tray arm to hold the lens when not in use.