There should be a lever for the PTO. This is where you select between 540, Neutral, and maybe another one or two more PTO speeds. Let's stay in 540 for now.
You'll need to press the clutch, select the PTO gear and release the clutch. This should get the PTO working.
If you still can't get it to work, try upload some pictures of the controls on your tractor, so we can help you. I tried to look online but there is very little info about that model.