To use this extension, you have to add
the following lines to your LocalSettings.php

require_once("/usr/share/mediawiki/extensions/Math/Math.php");
$wgTexvc = "/usr/share/mediawiki/extensions/Math/texvc";

In addition, make sure the variables $wgMathDirectory,
$wgMathPath and $wgTmpDirectory are set, as well as the
more general variables $wgEnableUploads and $wgUploadPath
according to your wiki instance.

For more information, see http://www.mediawiki.org/wiki/Extension:Math