An activation code is needed to watch YouTube on a smart TV. The YouTube app is also necessary.
After adding the YouTube app to a smart TV, navigate to the app's sign-in screen using the instructions provided with the TV upon purchase. An activation code appears. On a separate device, navigate to YouTube.com/activate, and enter the code exactly as it appears. Users may be prompted to sign into the YouTube account prior to entering the code unless previously signed in. Once the code is entered, click on Allow Access. YouTube should be accessible on the smart TV, and a confirmation screen should appear on the app screen.