Create a hyperlink on one of your web pages.
Point the hyperlink to your .doc file.
When a visitor clicks the link, they will either be prompted to download it or it will open up in Word automatically.
If you want to make sure it is only ever downloaded, Zip the document and link to the zip file on your web server.
I'd suggest making a folder on your web root and call it downloads. Put any files you want to offer for download into that folder, which keeps things tidy and manageable - a real benefit if you start offering lots of files for download.
Make your hyperlink and point it at the relevant file in the downloads folder.
If you supply details of the web designing software you are using, one of us will offer specific steps on how to do it, but the basics remain the same no matter which program you use.