Go here download the latest (3.4.05) version. Follow the read me file instructions. Before you upload make sure that you also include the latest security fixes.
If you don't have FTP, and a basic understanding of it, then you won't be able to set up or run a forum of this type. You may want to consider something like a Yahoo Group.
Update what? Could you be a little more specific in what you need? (I don't want to sound rude, I just don't understand exactly what it is you are looking for.)
Admin: has access to admin tools as well as being able to moderate all forums and set up forums etc etc Moderator: can usually only edit topics within forums as set by the admin Member: can only edit their own posts
But I don't quite get what you're on about either... if you've set up a forum the user you used to set it up is already admin by default...