It all depends on what you want to accomplish.
Usually you mount the degree wheel to the crank - to index the cam properly, or re-mark timing marks.
You need to make sure to set the wheel to exact TDC, not the damper indicator - which can be off as much as 5, 6 or more.
Use a piston stop (make or buy it,) pointer (piece of wire). Rotate the engine by hand until it stops, note the reading, Turn it backwards until it stops - note reading -- 1/2 way between is exact TDC - move crank to that spot, and set the wheel to 0. Now it's usable.
Then do whatever you are trying to do.
For help on degreeing a cam, internet search Crane Cams instructions - good info. You'll need a dial indicator with magnetic base, pad of paper, paint marker, and cam card.