Much like a house uses fuses to protect against shorts, burnt wiring and other common electrical mishaps, your car does as well. It's important for drivers to know where the fuse box on their car is located and how to replace a fuse in case it is blown.
Unlike other car parts, fuses don't wear down over time, and they don't really require maintenance. The only time you'll have a problem is if the fuse blows due to a short circuit. In this case, it's a simple matter of locating the fuse that's blown and replacing it. The symptoms of a blown fuse are easy to spot - typically, one or more electrical systems in your car will simply stop working, but the others will be fine. So if your power mirrors aren't moving, for example, but the rest of the car is fine, then the fuse box should be the first place you check.
Two common locations for fuse boxes are under the hood of the car and under the dashboard, but you may have to check your owner's manual for the exact location, as it varies depending on model. Typically, the fuse box under the dashboard will be right above the driver's left knee, hidden by a panel. Each box is responsible for different areas of the car. Both of them should have labeling that will indicate which fuses control each part of the vehicle.
Open up the fuse box and locate the fuse responsible for the part of the vehicle that is causing you problems. When you remove it, you should be able to see if it's blown, because it might look slightly blackened or burnt out. However, not all blown fuses will look this way, which is why you may want to instead use a test light/circuit tester to determine if the fuse is faulty. These testers are also useful for checking many fuses at once without removing them. If you don't have a tester, it's possible to remove fuses by hand, but it's probably easier to use the fuse removal tool, which is included in every fuse box.
It's then simply a matter of taking your blown fuse to an auto parts store and finding a replacement. Be sure to note the amperage that the fuse uses - this should be clearly labeled on the fuse itself. Never replace a fuse with one of a different amperage. It might be a good idea to invest in a box of assorted fuses, with various amperages. As long as these fuses are the same type that your vehicle uses, it'll save you a trip to the auto parts store next time something happens with your car's electrical system.