If you need to publish it on a site as a link for people to download, you
will need to upload the PowerPoint file to your web account, then on the
site, have a code like this: <a href="abc.ppt">Download this file</a>, where
abc.ppt will be the filename of your PowerPoint file.

There are also others way to publish your PowerPoint file on the web. Check
this out: http://pptfaq.com/index.html#name_WEBifying_your_PowerPoint