In the dreamhost panel (http://panel.dreamhost.com)
did you set up the domain:
Domains -> Manage Domains
If you see your domain in the list, make sure your files are in the correct folder, otherwise if it isn't in the list click this: Add New Domain / Sub-Domain
then fill out the form, and it should take at most ah hour till it works, then upload your files to the directory that was created.