In the settings tab on admin page. I don’t remember them on the top of my head but it should be very descriptive i.e. enable_names and full_name_required
The forum only stores the name that users provide and performs no “legitimacy checking” on that name whatsoever. Moderators (and admins) don’t get any more access to the “full name” field than any other member of the forum unless you disable display of it in the UI.