What sdayman is saying is that to set up hosting for this domain you must first log into the Panel > domains > manage domains. Add a new domain co.za. Fully host this domain. Now add an other domain/sub-domain streetcrew.co.za. At this point I believe you can remove co.za from your hosted domain list (but I might be wrong on this point).
The reason you have to do this, is streetcrew.co.za is technically the sub-domain of co.za - and with the DH system you have to add the main domian first before you can add a sub-domain. This stems from an American way of thinking, as domains here go like example.com. so before you can add sub.example.com you've got to put example.com into their system. I understand that this isn't exactly the situation with your domain in question - but that's what it looks like to the automated system.
Hope this helps.
EDIT: after reading your above post, I understand we're talking about different things. You can not register that domain with Dreamhost. You can however host it with Dreamhost. You will need to update your registrar to point the domain to DH - by chaning the name servers to ns1.dreamhost.com ns2... and ns3...
Registering a domain means you own the name and can point traffic to a specific server for content.
Hosting a domains means you're paying for space on a server to deliver your content to visitors.
Does that make sense now?
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