Hi Steve,
- Create the object you want to be the "button"
- Select the object
- Click "Link" in the plugin
- Now a clickable areas layer will be created and a "hotspot" placed on it.
- Enter the URL
- Review!
Here's a video tutorial if you are having problems: http://www.youtube.com/watch?v=Y5zuosXW_sQ&feature=channel
//Anders