I have just downloaded my digital copy of a movie (Star Trek). i live in the country and have so/so DSL service. The extras included timed out and stopped and I did not receive. There is a photo, but nothing happens when I click on it - what to do??

I live in the country and have slow DSL. I downloaded a digital movie on a MAC into iTunes. The extra's of the movie "timed-out". Stopped half way done. There is the picture only (that you would click on) - BUT, there is nothing there. How do I go about redoing to get the extras? I am pretty sure the movie loaded. There are two separate files. I am just looking on how to "redownload" a digital copy...Any options?? Thank you