Implement WP Supersized plugin in custom theme

Hi there!

First of all, thanks for making such an awesome plugin!

It works brilliantly when I use the theme Twenty Eleven, but when I try my custom theme, which I’m building, it fails.

http://jorisschaap.nl/test/?page_id=39

Is there some code of file I should add to make it work? How does it find its way into my theme?

I’m still a novice so I might have overlooked something abvious. I have searched all forums however.

http://ww.wp.xz.cn/extend/plugins/wp-supersized/