Edit ''Added_User' fields

My Zoho database has been public to date but I'm adding a private view of data that was entered via public pages.

The Added_User fields that I use to restrict users to seeing only their own data, is therefore set to 'Public'.

I'd like to edit this field so that it shows the user e.g.firstlast, otherwise users will not be able to view or edit data they have already entered via the public page.

Although I can see the Added_User field in the view, I am unable to edit it in the record view.

As Administrator is there any way of doing this?

Chris