How to Add Ads to Tumblr

1. Decide how you're going to deliver ads on your Tumblr blog. You can sell ad space yourself by approaching businesses and other website owners directly, or by using an automated service that delivers ads for you. Services like Google AdSense at Google.com/AdSense and Project Wonderful at ProjectWonderful.com allow you to create ads on your page without interacting with businesses. Both services require you to apply and be approved before setting up ads.
2. Generate your ad code, if necessary. In Google AdSense you can create a new ad unit under 'AdSense Setup' > 'AdSense for Content.' Once you're approved as a publisher with Project Wonderful, you'll receive an email with instructions on how to set up your ad box.

3. Open your Tumblr's customization page by opening your Tumblelog -- clicking your username at the top of your dashboard -- and clicking the 'Customize Appearance' button. You can also visit the page directly at Tumblr.com/customize; if you have multiple blogs on Tumblr, append that URL with your username, e.g., Tumblr.com/customize/username.
4. Consider choosing a theme with a sidebar, over one that displays your description and HTML area at the top of the page. Sidebar layouts are more common with blog layouts and set the ads beside your content. You can choose from dozens of free themes under the 'Theme' button on the top navigation bar.
5. Click the 'Info' button and paste your ad code into the 'Description (or HTML and widgets)' box where you want the ad to appear. If you're using images hosted on the Web, either by yourself or the advertiser, you can create a basic image ad with a link and the image using:



6. Save your page when you're done.