When worksharing is enabled, unless you change your user name in Revit, the Windows log on user name is used. If multiple users log on to Windows on the same computer, the currently logged on Windows user name is used for the Revit user name.
To change the user name in Revit:
This user name setting is stored in the Revit.ini file, which is located in this folder:
%APPDATA%\Autodesk\Revit\<product name and release>
Because this folder is shared by all the users on a computer, changes made to the Revit.ini file, including changes to the user name, affect all users on that computer. Therefore, if you change the user name in Revit, that user name is used regardless of who is actually logged on to Windows.