Before uploading app , you must have to change app name.You can choose app name by your wish.It would be shown in smartphone below app icon
Follow the below steps
Copy the image / app icon you want to use for your app.
Click on "app" in project pane in Android Studio.
Then expand the "res" folder in it.
Right click on "drawable" folder then press "Paste" option , it would paste that specific selected picture into drawable folder.
Now open app>manifest>AndroidManifest.xml and write your required icon name in "android:icon=@drawable/write_your_icon_name_here".