How can I redirect a domain added to Multi-Domains instead of it going to the default register page?

Being able to add more than one domain to wordpress is good, but my intentions were to have the second domain I added to be its own site under my network, example: goes to primary site. should go to completely different site, but under network, just as a subdomain would.

So I don't want to use for it, or have to "create" 'www' as the subdomain, because without the 'www', would still redirect to the default registration page in the primary domain ( which is disabled anyway.

How do we do this?

Thank you for your prompt response.
- Santi