If it's like the C220, you need to pry it off one side at a time. One each side there is a little tab that fits into a hole on the lower part of the wiper arm. I started to use a screwdriver and then thought the better of it because of the danger of scratches.
From the driver's side, I got my fingers on my right hand under the upper side of the cover and was able to pry it up enough to get the tab out of the hole. I then rotated it a bit to the left, did the same on the lower side ...
It basically snaps back on.