If you have it save to your computer just open iTunes and select Movies. Then goto top of screen on upper left and click file drop down box will show up. Look down and find add a file or folder. Click that and select the folder or movie in the folder and it will add it into itunes. Then when you connect you devise goto movies tab at top center above devise name and click the movie button then put a check mark in the box to add to devise.
Hope this helps.