1. Sign into your WordPress site that has the Thesis theme, if you are not already signed into the site. Once signed in, you will be in the WordPress administration dashboard of the site.
2. Click on 'Plugins' from the sidebar of the dashboard. This opens the plugins page of the dashboard. Click on 'Add New' to add a new plugin.
3. Type 'Thesis OpenHook' in the search field and click on 'Search Plugins.' When the results appear, click on 'Install' under the name of the plugin. This automatically installs the free Thesis OpenHook plugin. Once installed, an activation link will appear on the screen. Click on 'Activate' to activate the Thesis OpenHook plugin.
4. Click on 'Appearance' on the sidebar to reveal the theme options. Click on the 'Thesis OpenHook' option, which brings up all of the items you can edit on the Thesis theme.
5. Scroll down the page until you see the 'After Title' section. Once you get there, place your ad banner code in the text box by this heading. Both HTML and JavaScript code can be placed in the text box. Once you have entered the code into the box, click on the 'Save' button. This places the banner above the header.