When your iPod is connected and you click on the iPod in the left side you should get a screen with a bunch of tabs across the top. One of them should be for movies. You need to click that tab then tell it to load your movie or movies (if you haven't already done this).
I don't have one connected so I'm writing this from memory.
thanks i figured that out after i posted this. Now i need to get a refund from itubes, i rented it again before i discivered how to do it i was read somewhere you should'nt be charged