From Georgetown University Commons Knowledge Base
How do I activate the Capability Manager plugin?
Only administrators of a blog can activate plugins. If you are not a blog administrator, please contact the administrator of your blog to activate the plugin. Assuming you are a blog administrator, please login to the administrative side of your blog. Click on the plugins link from the sidebar on your left. Once you are on the plugins page, find the “Capability Manager” plugin from the list of plugins and click on activate. After you have activated it, click on the “Users” menu in the sidebar on your left. Under this menu, click on the “capabilities” link to edit the capabilities for a particular role.