[Zope] LoginManager, User Sources, ...

Hi! I searched the archives and found some entries, all concerning the same problem ... I read this: "LoginManager currently comes with a default User Source called Generic User Source (GUS), that is a GUF-like roll-your-own system. It uses GUF-compatible methods (userExists, userRoles, etc), so converting any GUF-using site to a LM site ..... " and wondered where this GUS is hidden and how I actually add users ?? (I'm still a newbie and want to know how it works!) Can somebody please help? TIA Wolfgang