If you subscribed to Smithsonian Channel Plus via Apple TV Channels, it's easy to subscribe to CBS All Access. You can try it free for 7 days, and after that, it's only $9.99/month. Please note that you'll be billed via iTunes.
- Open the Apple TV app.
- Search for the CBS All Access channel (you may need to scroll down your screen, where it's listed under "Channels").
- Tap the "Try CBS All Access Free" button.
- Confirm iTunes billing information.
That’s it! You now have access to the CBS All Access channel on Apple TV Channels.