The DreamHost part is easy. The more complex part is how the .uk registrar handles it. Bottom line is that you need to register the domain and when you do that, set the name servers to ns1.dreamhost.com, ns2..., ns3... This step varies with the registrar used.
Once it's registered (or even before), you can create your fully hosted domain here and it'll be reachable in a few days once DNS propagates.