To enable this feature, simply open your wp-config.php file located in your WordPress root folder. Then add the following line anywhere in the file: define(‘WP_ALLOW_MULTISITE’, true); via How to enable Multi-Site option in WordPress 3.0.
WordPress® 3.0 offers a new feature called Multisite that lets you host multiple WordPress blogs with one WordPress installation. This feature was formerly called WordPress Multi-User (MU). Enabling this feature requires an advanced level of understanding of configuring WordPress, and we do not recommend enabling it unless you are comfortable editing your wp-config.php file. NOTE: […]