Similar to the app icon, you may also want to replace the placeholder launch image:

In the Xcode project navigator, select Assets.xcassets in the
Runner folder. Update the placeholder launch image with your own launch image.

Verify the new launch image by hot restarting your app. (Don’t use hot reload.)

Create a build archive and upload to App Store Connect

During development, you’ve been building, debugging, and testing
with debug builds. When you’re ready to ship your app to users
on the App Store or TestFlight, you need to prepare a release build.

Update the app’s build and version numbers

The default version number of the app is 1.0.0.
To update it, navigate to the pubspec.yaml file
and update the following line:

version

1.0.0+1