Moving My WordPress Site from Development Folder to Live domain name

I have been working on a new web site design using the MU theme. I created a folder on our FTP server so that I could work on it without it being live. We have our domain name pointed to the main index.html file I guess. How would I go about moving this WP site to be the main site and do away with the old/main site that is there now?

Would I just point the domain name to the home page of the WP site or can I move all the files to a new folder? What should I do?

Thanks