Add the following to your LocalSettings.php file

### Google AdSense Extenstion ###
require_once( "$IP/extensions/mediawiki-google-adsense/GoogleAdSense.php" );
$wgGoogleAdSenseClient = 'pub-4272474988067896';
$wgGoogleAdSenseSlot = '5426528782';
$wgGoogleAdSenseID = 'wikisidebar';
$wgGoogleAdSenseWidth  = 120;
$wgGoogleAdSenseHeight = 600;
$wgGoogleAdSenseSrc    = "http://pagead2.googlesyndication.com/pagead/show_ads.js";
$wgGoogleAdSenseAnonOnly = true;