Your app icon is your app’s identity and is used on the device home screen and in other locations such as settings. Upload a PNG or JPG square image to use as your app's launch icon. Recommended resolution is 1024x1024 pixels.
If your image has transparency, it will be given a white background. For Android, a small rounding of the corners of your image will be applied. This same effect is automatically applied to your app icon on iOS by the operating system.
For more information about app icons review Apple’s guidelines and recommendations https://developer.apple.com/design/human-interface-guidelines/ios/icons-and-images/app-icon/.