You can just upload the files using FTP, file manager or publishing software such as Frontpage / Expression Web to somewhere in your public_html folder. Then just include a link to the file and then when people click on it it will give them a choice to open or download and save.
Example:
PHP Code:
<a href="www.your-domain.com/your-mp3-file.mp3">Click here to download our MP3</a>
Hope that helps - Don't hesitate to post back should you need more assistance
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