The User's Manual will tell you everything on accessing and using the calendars.
The Admin's Manual concerns site admininstrators. It explains all about creating and managing calendars, categories and members.
How-To Create Your First Calendar concerns site administrators too. It's intended to help you creating your first calendar in a few steps, without reading the whole Admin's Manual.
Note that all the planned features aren't implemented yet, and non-implemented features aren't documented either. More surprises to come! ;-)