I'm not sure if websawner will allow you to upload files.
The basic way to do it is to upload the file to some webspace - it can be your webspace, or one of the many upload sites that allow direct linking, then in your web page, create a link to the MP3 file.
If you are interested in learning a bit of HTML, here is a great web-site:
http://www.w3schools.com/
It is probably not the easiest, but it is up to date and accurate. If you use Google, you should be able to find many tutorials to get you started, then you can use w3schools.com to fill out your knowledge and check that you are doing things the right way.
A lot of people find it easiest to start off in web design using a WYSIWYG webpage editor. One such (free) editor is Nvu (from the same people that make Firefox web browser).
http://net2.com/nvu/