As in most written instructions, you have to read between the lines. I hope my photos and extra details make your job easier. The instructions starts with a drawing of the front fender in place, over the tire, without giving you any hints on how to get it there.
I don't have a floor bike repair stand so I use my tow hitch bike rack to hold the 520 at a workable height.
Now to the rear fender. I started again by taking off all four stays. The fender then rolled right into place. I found it very easy to clip the plastic mounting clip in place after the fender was almost all the way in.