[Plugin: User Access Manager] How to Allow specific group write access to page?

I’ll start by saying this: I’m not completely familiar with WordPress.
However, I’m trying to assign user groups for an organization’s website that is basically divided by department. Each department (AS, GS, and CS) will need to be able to maintain the content on each their own respective page, but do not need full access to edit other pages.

I’ve created a user to test with and assigned them to a UAM group (GS). I’ve also changed the page access to this specific UAM group… which allows All to read/view the page but only group members to write/edit the page. Unfortunately, I cannot get it to work the way it was designed and I’m sure that it’s something that I’ve done wrong.

Anyone care to help a newbie with this very simple task?

http://wordpress.org/extend/plugins/user-access-manager/