It is a little hard to explain so I took a screenshot. here

Import the mp3 (or AIFF) to the library. View the properties on it. Give it a class. Use the code in the image. Should be pretty simple.

This is using Actionscript 3, I don’t know if it will work with earlier versions.

Here is the actual fla file.. Link

Here are a couple tutorials pertaining to adding sound in flash…
FlashGuide.org
iLike2flash
Tutorialized

gotoAndLearn has lots of good flash tutorials, including sounds stuff.

scroll down a bit and you’ll see “Actionscript 3 Sound Basics” and “Sound Spectrum Display” tutorials. both useful.

pretty much where i learned all my flash/actionscript 3 skills…..but i hate flash now.