onLoad Problem - Please Help!

I am relatively new to Flash. Recently used a game tutorial that was very basic. Perfect for me. All the action script was directly attached to Movie Clips or Buttons or contained in them. I have been trying to convert this to action script contained all on the main timeline and in one frame. From what I have read this is the way to go - makes sense to me. One does not have to hunt high and low to debug.

How does one convert the onClipEvent(load) in this case. I have tried to use the
movieClip.onload = function() {} but that does not seem to work. Any guidance would be appreciated.

Remember, keep it simple. I am not trying to be exotic, just get the job done.