A hard rap with the hammer at the location shown should dislodge the rotor from the hub. If not, try alternating hammer strikes back and forth from opposite ends of the rotor hat until the rotor breaks free.

If you miss the rotor and hit the wheel stud, you can damage the threads, requiring replacement of the stud.

Use the 3M Scotch Brite pad to clean the rust from the surface of the hub that contacts the rotor (where the wheel studs poke through the hub - see second pic), and to clean any shipping protectant from the new rotor's contact surface (the large flat outer ring surface where the brake pads contact the rotor)