tv.youtube.com/start on your mobile device: first, ensure you have the YouTube TV app installed. Open the app and sign in with your Google account. Then, using your mobile device's web browser, visit tv.youtube.com/start. You'll be prompted to enter the unique activation code displayed on your mobile device within the YouTube TV app. Once you've entered the code, follow the on-screen instructions to complete the activation process. This will link your mobile device to your YouTube TV account, granting you access to a variety of live TV channels, on-demand content, and features while on the go."