Or, Stuff Happens, so....
OK, so changing a flat tire is definitely not the most fun thing we could be doing. And it always seems to happen at the worst time. So it's best to...
BE PREPARED (as the Scouts say) Always have your vehicle owner's manual in the car, along with an inflated spare, a jack, a lug wrench, a flashlight, and a piece of bracing material such as a small piece of lumber.
HOW DOES IT WORK? It's probably not the best idea to attempt to locate the jack in the dark, on a highway with no shoulder. Just as mysterious, often, is how the jack fits into the body or frame. Be sure and keep the owner's manual handy for reference. Follow the recommendations in the manual.
And when it comes time to finding new tires, you can use the Shumaker Tire Selector Tool to see your options.