You need to use FTP to put your files on your web site.
There are numerous programs out there to help you do this, and my personal favourite is www.smartftp.com, although many others like WS_FTP.
But you can use Windows XP but I don't recommend it. It's not very powerful. If you just need a quick solution then go to My Network Place in My Computer. Click Make/Add New Connection. And enter the information you got in the welcome emails. (If you use Hotmail like I did, you might get quite a garbled email, so go to your Dreamhost Control Panel, then support, then support history, and you can see everything properly).
It should be fairly easy to create a connection (even more so if you use a FTP program).
Once you've connected, you have to go into the folder called domain.com (in your case it will be called mangl.org) if you put an index.html file there, it will get rid of the directory listing hopefully :).
Hope that all makes sense