How to mount the bell to a wall
The black back part of the bell is meant to be screwed to the wall.
Simply make 2 or more mounting holes in the rear of the back of the bell and make the necessary holes in your wall to mount the bell.
Depending on your location you can opt to drill a small hole to feed the bell cable into the backback and into the + and - terminals.
Once everything is connected, place the metal bell outer onto the pins and twist into place (clockwise)
Finally place the blank cover plate on the front