Unfortunately, DreamHost does not supply DNS services for domain only accounts, you need to have an active hosting plan under the account to use the DreamHost name servers.
However, you can use a free DNS service, such as Zoneedit, to point the domain at your web server.
Once you have registered for a free DNS service, you can configure the domain to use the non-DreamHost name servers by going to Domains -> Registrations in the DreamHost panel, ticking the checkbox under the Modify Whois? column, then click the Modify whois for selected... button. The section for changing the name servers is at the bottom of the resulting page.
Save [color=#CC0000]$50[/color] on all DreamHost plans using [color=#CC0000]PRICESLASH[/color] promo code (Click for DreamHost Review)