How to Apply FancyBox to a Topic Image

Hi

How do I get an image in a Topic to open fullsize with fancybox?

I have added the following code to the html view of the topic which opens the fullsized image in a new window but not in the same way that a picture does on a product page

<a title="" href="Image1.jpg" rel="lightbox-pd">
      <img alt="" src="Image1.jpg" width="300" />
</a>

Do I need to add the script somewhere?

Thanks

Rob