How to install and allow plugins on your Wordpress MU?
Be advised that WordPress 2.9 MU is no longer a separate project from the main WordPress branch. It is continuing development as part of the main WordPress 3 branch under the name ‘multi-site’ or MS. This means that you can get all the benefits of both WordPress and WordPress MU versions by using the latest WordPress version. To help you in the process of creating a multi-user website with the latest WordPress version we have created a detailed step by step WordPress multi-site tutorial available here.
In order to install new plugins and allow the other blogs to use them you should enable the WP backend Menus. This can be done via the main blog administrative panel Options tab Pic 6mu As soon as this option is enabled you can install new plugins via the plugins tab from the menu on the left:
If you would like to start your WordPress MU Blog in a few clicks, check the WordPress MU Hosting package.