This is where you set the stage size , color , and frame rate of your movie.
Choose File > New (Ctrl-N / Cmd-N) to start a new file.
Choose Modify > Movie to set the Flash movie properties. When the Movie Properties dialog opens (see figure 02:01), keep the default values for a 4:3 width to height ratio. For this movie, also keep the default frame rate (12 frames per second or fps) and the default dimensions (550 pixels by 400).
The only time I change the frame rate is when I know I can afford the increase in file size and download time. The frame rate also affects streaming. If, for example, I know my target audience is using 28.8 modems, 12 fps is good because it gives my images time to stream in. For a more broadband audience, I'll raise the frame rate to 18 or 24 frames per second.
Set the background color to black by carefully selecting the Background color and choosing black (the first color on the standard palette).