A piece of a sample storyboard -
http://www.boardmastersoftware.com/sample1.htm
this is probably a poor example of what it should be like (i got it by a quick google search) , but it will give you the basic idea - you need to have frames illustrating scenes from your animation, and for each frame, you need time markers, action descriptions, and any necessary technical comments (such as sounds, special effects, etc) There are no limitations on how many frames you need - but you'll probably want one for each camera or scene change.
Hope this helps