Changing a tire really isn’t too tough. The first consideration is stopping the vehicle in a safe place. Drive slowly with emergency blinkers on until you find such a place -- a solid, level area far enough off the roadside so traffic isn't a major threat. (Beware of soft, grassy areas and inclines.) Under a bridge on an interstate may be a good location because of the concrete surface and wide shoulder area.
Next, keeping the blinkers on, pop the hood up, put the emergency brake on, switch the transmission to park (to first gear if car is a manual) and turn off ignition. If you have emergency triangles, put them out approximately 50 to 75 feet apart.
Next, take out your most important tool, the owners manual, and look at the section on changing your vehicle's tire. The manual will tell you how to remove the jack and spare tire -- which should be properly inflated -- and where to place the jack under the vehicle. Before jacking up the car, loosen the lug nuts with a lug wrench. (If they’re too tight and you can't do it, seek emergency road service, because using too much torque with the wrench can snap the lug nut or strip its threads.)
Put the jack under the vehicle as instructed in the manual. Jack the car up, take out the loosened lug nuts, remove the tire and replace it with the spare, tighten the lug nuts firmly but not tightly, then lower the vehicle back onto the ground. Remove the jack and tighten each nut, targeting the ones opposite each other, not in circular rotation.
Once you’re outta there, replace that spare with a real tire as soon as you can. And finally, first chance you get, have your tires and alignment checked and place another spare in the trunk.