.mov won't import. Use .avi. You can import directly to the background node but it doesn't help in visualization. Take the single poly square from the Poser prims and scale it to the aspect ratio of your video. In Material Room add 2D Texture node -> Movie and use your .avi. If I recall correctly Poser will add enough frames to accommodate your video length if necessary. Your video will display frame by frame on the single poly square. Just zTrans it back a bit behind your figure. Swap to multi port view and add planes with other angles on your reference video if you have them.