Simpy put, get a premium account otherwise, don't risk it, it against google policy. (btw, if you naturally place more code in your page, the forth+ ads won't show, and no risk for you. back to your article, you misleading title, there is no "how-to"
I seriously think you should link back to the blog where you copied this from.. http://www.mybloggertricks.com/2012/05/display-four-adsense-content-ad-units.html