How to add additional users after initial setup of free enterprise class email hosting

How to add additional users after initial setup of free enterprise class email hosting

I have my own domain name and signed up to host email using the Free Enterprise Class Email Hosting.  During the setup process, I added 2 users, with the intent of adding more later.

Now that setup is complete, I can see where to add new groups, but not new users, when I am logged in with the admin email address.  Is it possible to add new users after setup, when using the free hosting?  Or do I have to delete the account and start over again, adding all users at once?

Thanks!