Properly inflate a tire by using an air pump to fill the tire to the vehicle's proper tire inflation level when the car is stopped on a flat surface. Inflate the tire with a gas station's air pump or a personal portable air compressor.
A vehicle contains its tires' proper inflation level on a sticker in the driver side doorjamb or within the owner's manual. Use a tire-pressure gauge to determine each tire's current air level in pounds per square inch. Add air until the tire is sufficiently full. Double check the air pressure with the tire gauge a couple times.