The referenced article was updated and removed the relevant details on how to do this. The needed details are in the process of being restored.
You want to add the operator username/password that you would pass with -a/-p parameters to the keyring file that you have the database username and password.
From the same environment where you previously generated the keyring file you want to run the KeyringImpl class again with the additional parameter of bix. Besides the database username/passwords from prconfig file with the bix parameter you will then be prompted for the Pega operator and password.