Derek,
There really is nothing to fit as such - you just stick the camera mount bracket to the windscreen near the rear view mirror and plug the power supply in your 12v socket (make sure it's the one that's live on ignition, not always) .
The cable is very long, so easy to hide all the way from lighter socket to the a-pillar, then up and to the centre of the windscreen. I actually take a spare mount and power lead with me on long overseas trips and use the cam in hired cars - it's that simple (all you need is a new sticky pad).
If you want to go for a hard-wired setup (and you really don't have to), then get your feed from the same 'live on ignition' socket - there's only the lead and fuse to hide, no separate PSU/converter.
When mounting the holder, it's a good idea to hook the cam to any RCA video-in capable display, just to make sure it's the best position for the camera - the sticky pad is basically a single use and very strong bond - you'd need a new one should you decide to change the position of your dashcam.