Feel behind the clutch release arm, I'm thinking there is a 2 finger clip that holds it on the pivot stud. If you used your phone to take that picture, reach in a snap a pic of it on the back side. Pivot stud should resemble a ball stud. Looks to be a spot weld there beside the indentation on the arm that would suggest it holds such a clip in place.
The clutch release arm I believe should be pushed towards the input shaft to get it off. A good open hand bump or two on the end should do it, or a wooden 1" X 2" X 12" -18" long pry bar out of wood to keep it from slipping on the steel would also work. Should be enough relief formed in that arm to let it move in that far to jump it off. Once the clip is jumped off the ball stud, it should slide right off.
Might be an idea to take a pic once you have it off showing that ball stud to show others who may have the same problem someday. All DIY'ers learned somehow, most didn't have the internet and forums like this one to go to, to ask questions.