Apple simplified the screenshot submission process for iOS

Now it’s easier than ever to deliver your screenshots and app preview using iTunes Connect. Submit just one set of screenshots and one optional app preview per device family, and they will be used across device sizes and localizations.

If your app’s UI or behavior changes based on device size, or if you would like to include localized screenshots, you can use the new Media Manager to add custom screenshots. Learn more by watching What’s New in iTunes Connect from WWDC16.