Hacker Help: HEKTAR Apply light bathroom

Materials: Hektar apply

Description: Hello. I would like to transform this spot-clamp light bathroom, above my mirror, but it is a clip, I do not know how to fix it on the wall. I would like to put 2 or 3, just like the picture on the other fixture (this is just to show the system).

Also, my electrical box flush with the wall, so I have to hide … And I can not pinch the mirror because they are too low … Do you have any ideas?

~ Mymakao, France