For most cars, it is very easy to change the air filter, according to Edmunds.com. First, make sure the car is turned off and that it has cooled down. This is important, as the filter is near parts of the engine that get very hot when the engine is running.
Locate the air filter. The air filter casing is generally a large rectangle or square-shaped piece of plastic on top of the engine. Next, remove the clips, clamps or wing nuts that holds the casing in place. Once the casing is removed, gently take out the old air filter, and dispose of it. Then, set in the new filter, and replace the casing. Since not all cars have replaceable air filters, it is important to check the owner's manual before servicing any car.