Apple activates single sign-on for iOS and tvOS beta testers
What this means for users is that they won't have to sign in separately in every Apple TV app, if it's supported by the same cable company. Instead, the login credentials will be provided once for every TV service provider and every Apple TV app that requires specific logins will be able to tap into the stored info and verify the user's access. For example, if your cable provider supports Syfy Now, FOX Now and Watch ABC, you won't have to authenticate three separate times, if you've entered your cable credentials in your Apple TV settings beforehand.
This should also make watching TV on the go far easier, since none of us really keeps their cable TV credentials in their wallet. And with this new feature, we won't have to, since our iPhones and iPads will just authenticate with the saved login information.
If you are a beta tester and you have the latest tvOS and iOS beta builds installed, you can access this new feature either through your Apple TV, or your iOS device. For tvOS simply navigate to Settings > Accounts and look for the TV Providers section. For iPhone and iPad, go to Settings > TV Provider and insert the login info for your cable service there.
If you're not a part of the public beta testing, however, you will have to wait for the official release. It is rumored that it will be happening at some point in December this year, but Apple has yet to confirm or deny this officially.