Yt.be/activate from James Core's blog

On a computer or mobile device, open a web browser and go to the official YouTube activation website, which is usually yt.be/activate. Please ensure you are using the official website. On the activation website, you will be prompted to enter the code displayed on your TV screen. Once you've entered the code, follow the on-screen instructions to complete the activation process. After successful activation, your YouTube account should be linked to your device, and you should be able to access YouTube content on your TV or other device.