I don't have my regular computer in front of me right now, but I know that on my personal website, I have a root directory. I just created a forum to see if I could get into any HTML editing and check the root directory, but it doesn't look like that is an option for that particular service they are offering. You may have to "own" the forum (like Karen and Paul do) in order to change/add to the root directory. From what I remember, the directory is just a listing of all the pages on a website...and you can edit from there I assume (probably on FrontPage or whatever website software you would have)...but I didn't find anything on your forum server's admin that would allow that.

I could be totally wrong, but I think that is what I've discovered. Maybe someone else will be able to give you a little more information