The Network or MultiUser is a feature of WordPress that has been around (as the WPMU) for a while but in WordPress 3.0 series this has become part of the core code.
We settled on using subdirectories rather than subdomains so as to keep the www.lifesignpress.com unchanged in each URL. To enable this we followed the instructions at,
http://codex.wordpress.org/Create_A_Network
We had to drop our old Life Sign Press site and as it didn’t have much on it we just created a new MySQL database and edited the wp-config.php file to point to the new database name and we added in the option,
define(‘WP_ALLOW_MULTISITE’, true);
Pointing our browser at the root of our site we got the familiar WordPress installation prompt. It installed in the single click as usual.
Once we had the Network installed we added a new site (this /development one) to test the functionality.