My Book World NAS - how to allow Public folder read-only access?

I have a My Book World and simply to allow public access to the /Public folder, but READ-ONLY.
How can I configure this?

I want to create an additional user that has full access rights to the folder.

Is that possible at all? Because: when I enable public access to a folder, I can no further add users (makes sense).
And if I disable, I cannot add an anonymous user with empty password (because you cannot create such a user in the ui).

Is it possible to modify the user credentials via ssh? So I could force add an anonymous user without a password to the config?