1. Pre-installation tasks

phpBB3 is an web application programmed in php, it need next tools to works fine
* An http web server (Apache)
* A database (MySQL, postgreSQL)
* PHP5, with modules required by phpBB3 (php5-mysql ou php5-pgsql)
* php5-ldap
* phpCAS is also required.
On the same machine, or on other hosts, you need at least an LDAP directory, and a CAS server if you want to offer single-sign-on authentication.

Then install phpBB, this is easy to install, just follow next guide : phpBB Userguide.
Very important :

If you wish to use LDAP or CAS authentication with phpBB3, your phpBB3 administrator must have an existing entry with same             login in your LDAP directory.
Next, we'll assume phpBB3 is installed on a webserver with FTP access. $PHPBB_HOME is the root directory of your phpBB3 instance on this machine.

CasLdapAuthBB has been validated with phpBB 3.0.1, phpCAS 0.6.0-1, running under Apache 2, PHP5 and MySQL5. LDAP directory was OpenLDAP, and CAS server CAS 2.0.

2. Installation

Detailed information about phpBB MODX installation can be found here :
[Mods installation guide|http://www.phpbb.com/community/viewtopic.php?f=69&t=724145]

You can also unzip the archive, open file *install_casldap.xml* with Firefox and follow the instructions displayed in your favorite browser.