On a Mac: go to File, Open. Find the movie you want, and click Open or Choose near the bottom. It will be under either Movies or TV shows.
On a Windows: Nidesoft iTunes Converter is an excellent Video to iTunes Converter tool which could convert Video files to iTunes movie. It could accept almost all the popular video formats as input and support video to all the Apple devices, including Video to iPod, Video to iPhone, Video to Apple TV.
//// on a Windows //// First, iTunes supports video format: .MP4, .M4V, .MOV, H264 etc. So, if you wanna import movies into it, you need to check if ur movies format is right, if not, you'd better convert them to suitable format. recommed Daniusoft video converter, famous brand, worth trusting !
PS: Daniusoft Ipod transfer - transfer video/music files during ipod, iTunes, computer easily and quickly.