To authorize Xfinity, visit xfinity.com/authorize, sign in with your account, enter the activation code from your device, and follow the prompts to complete the process.
 
How to authorize Xfinity?

To authorize Xfinity, follow these steps:

• Go to xfinity.com/authorize on a web browser.
• Sign in with your Xfinity account credentials.
• Enter the activation code displayed on your TV or device.
• Follow the on-screen prompts to complete the authorization.
• Once authorized, you can start streaming content.