The last build you upload to iTunes Connect and submit to the App Store should be product quality and pass iTunes Connect validation tests.
Before submitting your final candidate, go to App Review to review the App Store and human interface guidelines. For watchOS apps, also read Preparing Your watchOS App for Submission.
You may need to enter additional information in iTunes Connect before you can submit your app to App Review. For the metadata that is required, read “Viewing and Changing Your App’s Metadata” and “iTunes Connect App Properties” in iTunes Connect Developer Guide.
In Xcode, prepare your app for distribution and then create an archive of your app.
Immediately after creating the archive, validate the archive and fix any validation errors before continuing.
It’s recommended that you submit a build you distributed for testing to App Review. For iOS, tvOS, and watchOS apps, upload your app to iTunes Connect and then distribute the app using TestFlight to test your builds. For Mac apps, distribute your app to registered computers or distribute your app outside the Mac App Store before you upload it to iTunes Connect.
To submit the final build of your app to App Review, read “Submitting the App” in iTunes Connect Developer Guide.