Once the tire is off the ground, unscrew the lug nuts of the tire completely.
Remove the tire from the mount of the car and rest away from the vehicle. Then, mount your new tire, aligning the lug nut holes carefully. Attempting to force the tire to sit on the car mount may result in destabilizing the car jack, causing serious danger.
Once the new tire has been placed onto the car mount, hand screw the lug nuts in a star pattern to avoid tire instability.