Once you have the source file downloaded, open it in Flash, the file name should be "ssound.fla"). To do this simply:
Go to File> Open
Navigate to where the file Is and click OK.
Now that you have the source file
opened in Flash, you're ready to go to the next step in actually
adding the sound file to the animation and making the final
version look (and sound) like the animation above.
Once the Flash file has been opened,
the steps below will show exactly how to make the sound pan from
speaker to speaker.
Follow these steps:
First Right Click on first frame in the layer marked "sound" and choose properties.
Once that has been done, choose the tab marked Sound, and you should see a screen like this: