Caliper piston

There are a couple ways but assuming this is not a caliper that has a parking brake included then it is not too complicated. Basically you need a C clamp, large vice grips, or large channel locks that can fit over the caliper and piston. Then just put the old pad on top of the piston and use the tool on the pad and back of the caliper to squeeze it back in. Just make sure you don't top off the brake fluid prior to doing this or it will come out of the cap.

Here is a guide that helps with this:

https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd

Lastly here is a video that we have that shows how to do both types of calipers:

https://www.youtube.com/watch?v=j8YwfSKEzZo

Let us know if you have other questions. Thanks