Do you mean the brake dust shield?
If yes, then it can be a bit of a PITA.
Follow this link to the maintenance section at the top of the page and go onto the brakes part and you will get the diagrams of the rear brake set up.
http://www.golfgtiforum.co.uk/index.php?topic=54324.0The disc has to come off, and then there are 3 screws to come out, am sure they are torx.
The old shield was rotten so it came off easily when the screws came out, with lots of WD40.
The problem is the new shield will not go over the hub, so I cut the straight bit at the front off on the new one (see the diagram), as I didn't want to take off the hub. Then cleaned it off and painted the edges that had been cut.
The shield was refitted with the 3 screws, disc back on and refitted the calliper.
Hope that helps.
Ps welcome to the forums