I'm going to assume you have registered a new domain name. Add your new domain name to be fully hosted. Log into ftp or shell and delete the newdomain.com folder. Then rename the olddomain.com folder to newdomain.com and that should be it. If you have a content management system (drupal, wordpress, etc) it's a bit more involved because you need to make new hostmasks and edit your configuration files to point to newdomain.com but it's pretty straight forward. As far as dreampress... idk about that since I have never used that service.