Once you have added the CBS All Access app, launch the app on your Fire TV, then follow these steps:
1. When the app has launched, use the remote to select "Settings", then "Sign Up / Sign In". You will be presented with a website and a code.
2. Using a web browser on a desktop, laptop, tablet, or mobile device, go to cbs.com/firetv and enter the code exactly as it appears from your Fire TV.
3. You will be prompted to login to your CBS All Access account. When prompted, enter your log-in credentials. When you have logged in successfully on the website, you will be logged in on your Fire TV.