For my 12-40 lens and 180mm dome port set up there are internal locks that keep the dome port, extension ring, and adapter connected. You need a small screwdriver or pen to manipulate the lever to unlock them.
The entire assembly then slides over the 12-40 lens and then is locked into place by the port lock on the side of the Nauticam Housing. From what Mobula say's it will also fit over the 7-14 lens
I can try to send images of the locking mechanisms tomorrow. Or maybe someone can locate an image online?