Forum:Wikipedia style

I would like to know how to make my wiki's skin look like the MediaWiki default monobook skin, as seen on places like Wikipedia. On wikia, Monobook doesn't look the same. It has an advertisment slot, rather than the Wikipedia and Uncyclopedia look and feel. If it isn't possible here, then are there any other MediaWiki sites with Monobook as their default skin which are the same idea as wikia?

http://images3.wikia.nocookie.net/__cb20100321155703/clubpenguinrocks/images/e/e6/G-animation.GIF 11:08, April 15, 2010 (UTC)