Bjorn, there is no such thing as a stupid question, silly mistakes are made through not asking for help though
That is the right Gates belt you have. I have the same on mine, if you have a squeaky belt they say changing to the 6 toothed belt minimises this without compromise, I don't have that problem.
If you stand at the rear of the alternator you will see the mounting bolts and there is a tension adjuster and the slot itself is toothed on mine which you slacken off to remove and replace the belt.
Once you start in it's quite obvious, when I renewed mine it was a fairly tight squeeze getting the old one off and fitting the new one but slack enough with ample adjustment when on.
About 1cm deflection on the longest run will do nicely without compromising the alternator bearings.
