It is very easy to create an add for your web-site in an AdSense Program. You only need to choose the size of an add and adjust colors according the color theme of your web-site. Then, you need to copy the given code and put it into your web-site template.
Remember, according to the AdSense’s terms and conditions you cannot have more than three adds and more than three blocks of links per one page. There is no catch, Google does not like catches.