There are tools that allow you retract the pistons after you’ve removed them from the rotor . Just also keep this in mind , brakes are t that hard to do these days just keep in mind the torque settings for the caliber bolts , brake clips if so required or the brake adhesive . And also be careful of the caliper seal as that’s the make or break of buying a new one . When I’m doubt let a certified tech do it , somebody with brake knowledge . Good luck