Next time try looking for a video that shows you how to do the job of changing the cabin air filter. Here’s a link to one for 2015 to 2020 Honda Civics.
[How To: Install a Cabin Air Filter on a 2016-2020 Honda Civic - YouTube]
After you watch the video you can decide whether you feel you can do this job. If you decide to try it go to a car parts store and tell them what you want.