As you've probably guessed, attaching a new cabin filter is pretty much just the reverse of the steps you used to take the old one out. But before you swap in the new one, take a few minutes to clean up the housing compartment and air intake duct. This will help sweeten the air inside your car and set your new cabin air filter on the path to enjoying a nice long life.
Once everything's cleaned up, pop the new cabin air filter into the slot left by the old one. Securely reclip or rescrew anything needed to hold the new filter firmly in place -- you don't want any air to be able to slip by unfiltered.
With that task complete, you can rest assured you'll be breathing purer air, free of allergy-inducing pollen and cough-provoking pollution. This is especially important if you or any of your regular passengers have respiratory issues that make breathing dirty air especially irritating or even dangerous. Typically you'll want to replace your cabin air filter about once a year, or every 12,000 to 15,000 miles (19,312 to 24,140 kilometers), although it doesn't hurt to take it out and shake free the debris from time to time in between replacements. If you live in a traffic-clogged urban center, you might want to change yours more often than if you live in a more rural setting. The harder you force your air filter to work, the faster it'll clog up.
Now that your car has a new air filter, you can breathe easy knowing you are, in fact, breathing easy. On the next page you'll find links to lots more great info about cars, car maintenance and motoring in general.