Once you have added the CBS app, launch the app on your iPhone or iPad, then follow the steps below:
 
1. Tap the "Menu" icon in the top left corner of the homescreen.
2. Select "Sign In".
3. Sign in with your CBS All Access account. If you subscribed to CBS All Access via your Apple TV/iTunes, you can also select "Restore Purchase" at the bottom of the screen.

You're now ready to watch CBS All Access on your iPhone or iPad!