It's not hard, but there are a lot of problems you may run into depending on what you're planning to do with the sound.
No matter what, make the sound be 44.1 KHz, 16 bit (either mono or stereo). Other bit depths are likely to fail to import, and other sample rates may lead to sync issues.
If it's an AS3 FLA, especially if you plan on synchronizing animation to the audio, keep the file as a WAV file.
If it's HTML5 Canvas, make it be MP3 before you import the file.