Use a wire brush to clean the rust from the core, then install the new rotor. Before installing the new rotor, brake it with brake cleaner, being careful not to touch the pressure surfaces with oily hands, then tighten the hub bolts.
Replace the pad to stop the sound
Remove the old pad and pay attention to the direction of the guide plate and wear indicator. The pad is held in place by a spring, so it isn’t too difficult to remove. However, if you need to loosen it, you can tap the edge with a screwdriver.