Here's how I installed my camera.
I fitted mine up behind the rear view mirror
I secured the power lead to the mirror stalk and pushed it under the head lining to the A pillar
I then removed the A pillar trim (there's a screw behind the airbag tag and then just pull the trim off), and secured the power lead behind the airbag. No photo of that bit I'm afraid but once the trim is off you'll see where to cable tie it
Run the power lead into the fuse box on the drivers side
I didn't want to cut the plug off the end of the power lead so bought the socket I linked to previously. If using the same sort of thing then cut the red crocodile clip off and crimp the piggy back fuse holder to the wire
Cut the black crocodile clip off and crimp a ring terminal on the wire and attach this to an earth point
I connected the piggy back fuse holder to a spare switched fuse way and fitted a 2A fuse
I then just tidied everything up
Hope this helps. Any questions then just ask away.
I'm guessing it would be very similar on a MK7 but I've never been in one so can't say for sure.