If Enrollment is enabled for the module (see Settings)...the next step is to allow enrollment for the Event (see Event Edit Form).  Once enabled for the Event, users in the correct role (can be any registered user - currently no support for anonymous), can sign up for the event on the "Event Detail" form.  Once they have signed up, admins (or moderator role) must approve the enrollment...when approving the Admin/Moderator can send an email stating they are approved;  Finally, the Admin or Event creator can pull up the "Edit Event" form to see how many user's have enrolled and send them emails or delete the enrollment.

The new version fixes several issues w/enrollment.

Hope this helps.