Hi @zivtech,
Welcome to the Auth0 Community!
Yes, that is correct. You will need to configure the additionalSignUpFields on the Classical Universal Login experience. It will not work with the New Universal Login experience.
First, I recommend checking this FAQ to learn more about configuring additional sign-up fields on the Classic Universal Login experience.
And then to edit the description, you can change the lock configuration object in the custom login page script, specifically the languageDictionary for the signUp object.
Please let me know if you need further clarification or help.
Thanks,
Rueben