Nelson A Li wrote :
Btw, Can enyone teach me how to install extensions?
this might help : http://www.mediawiki.org/wiki/Manual:Extensions ;-)
usually (sometimes it's different), you download it, you put the file(s) in the "extension" folder and you add (in LocalSettings.php)
require_once( "$IP/extensions/ExtensionFolder/ExtensionName.php" );