If you have to change a tire out on the highway make sure that you are well out of the flow of traffic. If you have materials to help people see you put them out and make sure that you only use the jack if you are on a hard flat surface. Using a jack on a soft surface such as sand can lead to the car falling off of the jack. Set your emergency brake and turn on your emergency flashers. Check the owners manual for step by step directions and safety tips for changing the tire. Take out the spare tire and the jack. If your car has wheel locks take the key out so that you can get it unlocked to change the tire. Loosen the lug nuts while the car is still on the ground. Put the jack under the car and start jacking it up. Remove the lug nuts and then take the tire off of the car. Set the tire aside and wipe down the bolts that the lug nuts go on. Then put the spare tire on. Tighten the lug nuts finger tight and then lower the jack so that the tire in on the ground. Tighten the lug nuts according to the pattern in the owners manual. Properly tightening the lug nuts is very important. In addition to the spare tire and jack keep a pair of gloves, a rag, and something to kneel down on in your trunk. Then go to the tire dealer and get your tire repaired or replaced as necessary.