Video in FlashMX

I have done this in the past, but I’m not sure what I’m forgetting! how do I place a film in FlashMX?? I could have sworn in the past I just imported it into my library & then when I dragged it to the stage it added the appropriate amount of frames, however, now it just puts one frame on the timeline and my movie clip doesn’t play… what am I fogetting?? Thanks!