A webpage or...

You need more advanced coding to create a forum. You need a database and a server side language such as ASP or PHP

Start from the beginning and learn to walk first. What youve asked can come out of the box so to speak, but if you do it this way you will never understand the principles behind web development/programming.
Craig

If you need instant results, get a web host with some sort of self-install scripts. For instance, the people I host with offer a little service called Fantastico (within cPanel), and in Fantastico, I can click one button and install a forum, or a content management system.

Otherwise, do it like the rest of us did, start by learning static html, css, php, etc. Eventually, you'll get there.