User Profile Linking in posts - 1.0 - How to activate

[essonyc]

I downloaded 'User Profile Linking in posts - 1.0' (http://mods.mybb.com/view/user-profile-linking-in-posts) and copied the only file within the .zip to my forum's root directory - as I had done with several other plugins. However, this plugin does not show up in my ACP so I'm not sure how to activate it.