yes, the simplest method to to do what your asking is to log into the domain registrar and change the nameservers for the domain to ns1.dreamhost.com, ns2.dreamhost.com, ns3.dreamhost.com
There are other ways, but above basically sets dreamhost as the DNS authority for the domain.
You can then add the domain as 'fully hosted' at dreamhost. remember this moves mail functions for the domain as well, so set up any mailboxes needed. It's possible to set mx records as well, so if you need to point mail back to the existing mail server you can do that as well.
Also remember that when you change your name servers there will be a propagation delay before the changes take place across the internet. this usually take 12-24 hours but could take 3 days to be seen worldwide.