1. Create your app icon.

2. Generate icon in 5 different sizes

72*72
48*48
96*96
144*144
192*192

4. Change the name of the icon to ic_launcher.png

5. Paste your icons ic_launcher.png based on their sizes in folders [PrjDir]/android/app/src/main/res/mipmap-*/.

72*72 ic_launcher.png in mipmap-hdpi.
48*48 ic_launcher.png in mipmap-mdpi.
96*96 ic_launcher.png in mipmap-xhdpi.
144*144 ic_launcher.png in mipmap-xxhdpi.
192*192 ic_launcher.png in mipmap-xxxhdpi.