Map SubD.Client.com to Client.Oursite.com = how?

How can we map
Subdomain.ClientsDomain .com
to
ClientUsername.OurDomain .com ?

We have ClientUsername.OurDomain.com set up already, but the worker system appears to be deprecated (?? per helpdocs)

I’m on a pretty basic plan, and we want to just get it working well, once we prove it out I’m open to upgrading if that’s required for scale.

Thanks,
Roger at http://SwiftCloud.AI