Upload the MP3 file of the song that you would like to have played on your user lookup to a file host website. Once uploaded, replace the "INSERT MP3 URL HERE" in the code below with the direct link to the newly uploaded MP3 file:
<bgsound src="INSERT MP3 URL HERE">
A good file host that I recommend is fileden.com. You can find others by Google searching "free file hosting."
Note: Music can only be heard if you are viewing the user lookup with Internet Explorer. Firefox users will not be able to hear the music playing. Also note that MP3 files are the only music file types Neopets.com accepts. All others will have to be converted to MP3, otherwise you will hear no sound when you visit your lookup regardless of the browser.