Next to a CalDAV server, you need access to a mysql or postgresql
database to use agendav.

Read /usr/share/doc/www-apps/agendav-${PVR}/installation.rst.bz2 for
installation instructions of the database.  This includes loading the
SQL statements from /usr/share/webapps/agendav/${PVR}/sqlscripts/.

Next you have to edit all config files in /etc/agendav/.

Before you can use agendav, you need to upgrade the database (even
though this is a new install) using:

  $ agendavcli dbupdate