Im just confused how to build this URL (easy question for you guys, I think)

[eluser]pickupman[/eluser]
You would need to use the [url="http://codeigniter.com/nightly_user_guide/general/routing.html"]Router[/url] class for this. Routing is for making a uri use a different pattern than the standard in CI. This would go in /application/config/routes.php

Code:

$route['infosystem/administration/user_management'] = 'infosystem/user_management/'; //URI without 4th segment
$route['infosystem/administration/user_management/(:any)'] = 'infosystem/user_management/$1'; //URIs with 4 or more segments