Updates are submitted to the Windows Store, just as you would with any other Store app. After approval, they can be configured to trickle out and/or force install (when available). More information can be found at https://msdn.microsoft.com/windows/uwp/publish/upload-app-pa...

You can also create a "flight group" consisting of your test team and only push out more broadly when your internal QA passes. Check out https://msdn.microsoft.com/en-us/windows/uwp/publish/package... for details.