For the plugin to work you will need eg the exec PHP plugin (http://bluesome.net/post/2005/08/18/50)
- Download and unzip the package.
- FTP the entire "ECadmanager" directory to your /wp-content/plugins/ directory on your blog.
- Activate the plugin on the "Plugins" tab of the administartion panel.
- Either use the widget, or place the template tag where you wish your ads to appear.
- Go to the new section of the WordPress admin, and fill in your seller id and seller secret.