You cannot sign in without an account. If you are on the bbc.com/tvcode page, look for a button that says "Register now" or "Create account." You will need to provide an email address, a password, and your UK postcode to verify your location.
If you entered the code on your phone and it says "Success," but your TV is still showing the code: bbc.com/tvcode sign in
If you are trying to watch BBC iPlayer on a smart TV, streaming stick, or games console, you may have encountered a screen asking you to visit to sign in. This is the official portal for linking your television device to your BBC account. You cannot sign in without an account