Admin Forum:Needing help with the MediaWiki pages

I've recently adopted a wiki and I'm still getting used to the admin features. I was wondering if someone could help me with the process of adding extensions to the: MediaWiki:Wikia.css, MediaWiki:Common.js and MediaWiki:Common.css pages because I want to add the ability to use the collapsible tables, tabs and etc. Also I was wondering if I was missing a page or two? And could you explain what the 'Wikia' and 'Common' do? I understand that the extension .js = java script and .css = cascading sheet style.

NeonRiser2134 (talk) 18:16, October 8, 2011 (UTC)

EDIT: If this question is in the wrong place, I'm sorry. As I already mentioned, I'm still new to things.

NeonRiser2134 (talk) 18:18, October 8, 2011 (UTC)