What tool, and HOW do you retract caliper pistons

Hello all, newbie here.

I have a Doge Ram pickup truck, and the rear disc conversion uses calipers that fit a 77-78 Cadillac Eldorado. It's time to replace the pads, and I was informed that the pistons need to be turned while retracting the piston? Can anyone direct me to a site that has instructions/photos, and what tool to buy for the job? I thank you all in advance. Take care.

You can buy a brake cube from any automotive store for it, but I find that needle nose pliers work just fine. All you have to do is open the bleeder valve and screw in the piston (clockwise). No pushing force is required, just twisting force.