If you want to link to an mp3 then do this:
Alternatively you can link to a page with an mp3 embedded in it. To embed something do this:
<embed src="abc.mp3" width="x" height="y" autostart="false">
It is not neccesary to include the width, height or autostart attributes but I did include them just so you know about them.
To put an image on page and position it you can do this:
<img src="def.gif" style="position:fixed;top:100px;left:50%;">
You can use px or % for units. px means pixels and % refers to the percentage width/height of the page. You can also replace top with bottom, and left with right.
You can also replace fixed with absolute to position it relative to it's parent element.