Display Names are a way to replace numeric extensions (i.e. 1324) with names, like 1324 - Rick Sanchez, or 1423 - Sales Hunt Group.  These can be configured by the Administrator, or they can be pulled from CUCM (VoIP Detective PRO only).

Display Names, while available in VoIP Detective Free, are only displayed in select locations to the Administrator.  For Display Names to be visible in reports, you must purchase VoIP Detective Pro (for more information, please open a support request).

To add Display Names for users, please go to Administration -> Display Names.

You can manually add up to 5 display names at a time:

And after hitting "Go", you'll see them listed, where they can be updated or deleted

If you have too many users to manually enter, you can sync them with CUCM.  For information on that, please see Synchronizing data between CUCM and VoIP Detective