I disagree with the advice given above.
Clean My Mac 2 -- not recommended, known to cause problems.
We recommend
App Cleaner (free) if you feel the need (not usually necessary) to delete all associated files with an uninstalled app.
In MOST cases (ie any app that doesn't alter the system in any way), you can simply drag the app to the trash and that's it. The 4K preference file that might be left behind isn't worth the bother. But in some cases, or for different reasons, people like to have the app be completely uninstalled (this is, I think, a leftover issue from Windows users but whatever). That's when apps like App Cleaner and App Zapper also delete the associated files, but the trick to using them is NOT to trash/delete the original app first. Drag the no-longer-desired app to App Cleaner or App Zapper instead of the trash, and it will find the associated files.