You mean a wizard to help you create your initial application. It creates a common icon and calls it ic_launcher.png and puts it in each of your available folders.
If you want to change your icon, just specify your ic_launcher file and size it in accordance with Google standards and place it in every available directory. The root of your project also has the ic_launcher-web.png file, which you must also replace.
If you want to use the generator to create your icon, you can use the Android Studio Launcher Icon tool here . Just create it and follow my steps above to configure it.
Finally, a note from Google about the correct icon sizes:
