Login to Adsense
Login into your Adsense account and click on the Adsense Setup tab. This will bring you to a page offering you three Google products:
– Search, content and referral.
Click on Adsense for content.
Ad Links or Ad Units
Which takes you to a page where you will choose the kind of ad unit you want to create. An Ad Unit has a title, 3 lines of text and an url, an image or both and redirects to a website of the advertisers choice. A Link Unit displays a list of topical links that brings a user who clicks on a topic to page of related ads. You can have 3 ad units and 3 link units per page.
Ad and Link units can be customized. You have a selection of sizes, colors and shapes. It is better; to try having the ad units match the colors and style of your website so that they blend in. This should result in a better click thru rate (CTR) from your visitors.
Choose the Ad Unit option and leave the default in place. Then click on the continue button at the bottom of the page. This will bring you to a page where can choose the size of your ad as well as the color. The sizes are numerous, from huge Leaderboards to small buttons. After you have selected your layout and color, click continue to go to the next page.
On the next page will be the actual code for your Adsense ad. Simply copy it and paste it in the web page code where you want the ad to appear.
After you have done this, simply repeat the process for each ad unit or link unit variation. The link unit has slightly different options but the process is essentially the same.