Once you’ve added Paramount+ to your SHOWTIME subscription, you will need to link your SHOWTIME username and password with your Paramount+ username and password. To do so, go to paramountplus.com/showtime or click the 'Activate Now' button upon signup. Create a new Paramount+ account or enter your existing Paramount+ credentials and follow the instructions to link your Paramount+ and SHOWTIME accounts.
NOTE: If you were a CBS All Access subscriber through SHOWTIME and have already activated your account, you do not need to re-activate your subscription. You can continue to log in to the Paramount+ site and apps with the same linked account you used for CBS All Access.