How do I compress the rotors to fit new pads

Hello,

Before you can install the new pads, you will have to compress the caliper pistons back into the housing (not the rotors). This can be done using a large C-clamp. Before compressing the piston, you will need to remove the brake fluid reservoir cap.
If you are replacing the rear brake pads, then you will need a special tool in order to push the piston back into the caliper. That tool will line up with the notches that is on the piston and turn the piston to retract it back in.

Here are couple of helpful articles:

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

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.