I assume your friend only has the domain registration under his DreamHost account, no hosting plan? If so, then unfortunately DreamHost does not offer DNS services for accounts that do not also have a hosting plan.
However, what your friend wants to achieve is still possible by using a free DNS service such as ZoneEdit.
The first step would be to obtain the free DNS service and obtain the name servers you will need for the next step.
Then you configure the domain to use these name servers by going to Domains -> Registrations in the panel, tick the checkbox for the relevant domain under the 'Modify Whois?' column then click the 'Modify whois for selected' link. At the bottom of the resulting page you will see 'Set DNS info to host your domain elsewhere', this is where you enter the name servers.
The final step would be to use whatever configuration utility the name server provides to add the main A-Record for the domain and (most likely) an A-Record for 'WWW' as well, pointing these A-Records at the IP address of where the site is hosted.
I hope the above makes some sense.
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