Stephanie
To add a video to the back of the main page try the following:
1) In the Create Disc area select new
2) the icon at the top just to the right of save is "replace background image or video", click and add a mpg file that you have created for your background, answer question about all pages, just select main for now
3) Enter preview mode in menu designer (icon to the left of font names)
4) click play at the bottom to see what you have done
5) return to edit mode in menu designer
6) use "select video effects in menu buttons on the lower right to add an effect like zoom out and adjust controls as desired
7) save and name
Is that what you want?
Jeff