I'm a novice driveway mechanic.  Last weekend I took the old front disk
brake pads out and was trying to replace the pads with new ones.
However, I wasn't able to push the piston back in to fit the new brake
pad in.

This coming weekend, I was planning on giving it another try using a
C-Clamp.

Do I have to take the brake unit off of the rotor in order to squeeze
the piston in?

Do I have to use a clamp to push the piston in, or can I use a wooden
stick or something jammed between the rotor and the piston to wriggle
the piston in?

I didn't take the brake unit off from the rotor mounting in my previous
attempt.

-- Craig