For Android 3+:
In the Project window, select the Android view.
Right-click the res folder and select New > Image Asset.
If your app supports Android 8.0, create adaptive and legacy launcher icons.
If your app supports versions no higher than Android 7.1, create a legacy launcher icon only.
In the Icon Type field, select Launcher Icons (Legacy Only) .
Select an Asset Type, and then specify the asset in the field underneath.