Go to panel.dreamhost.com, log in, go to the main menu on the left, click domain, then click manage domain, then find where it says plumsaplomb.com, and go to the column where it says Web Hosting, and under that in the row plumsaplomb.com click on edit under "Fully Hosted", then go to "specify web directory", type in your new home directory of plumsaplomb.com/indexhibitv070e. Hope this helps and is what you were looking for.
Also you wouldn't want to upload your files to a directory called root, the root means the beginning directory. For example if you had two pages, index.html and detail.html on the domain plumsaplomb.com you would upload the file index.html and detail.html to home/"username here"/plumsaplomb.com/ and that is your root directory. The root you were trying to access was the root of the whole server, not YOUR root directory.