Here are the steps on using Xcode’s Devices window to capture a screenshot of your device’s screen, which is connected to you Mac.
- Run your app on your device.
- On your device, configure the screen the way you want to capture it.
- In Xcode, select Window/Devices.
- In the Devices window (see image below), select your device and click the Take Screenshot button.
The new screenshot appears on your Desktop. Use it any way you see fit. For example, you can upload it in iTunes Connect.