Hello Marcb1992,
It sounds like you have made a movie purchase that contains iTunes Extras and you cannot find a way to download them. According to the following article you should be able to Check for Available Downloads to get that content downloaded:
About iTunes LP and iTunes Extras
http://support.apple.com/kb/HT3823
Titles with iTunes LP and iTunes Extras may be purchased from the iTunes Store with an iPhone, iPad, or iPod touch. The primary content for an album or movie will download directly to the device; the iTunes LP or iTunes Extras will download to iTunes on your computer when you choose Store > Check for Available Downloads. This requires iTunes 9.0 or later.
Thank you for using Apple Support Communities.
Take care,
Sterling