more as one domain on a virtual host

[dotbizz]

hi-

my problem is very simple - having not in a confixx. Now i am swiched to plesk and i am a little confused.

If i create a webspace, the system ask me by the domainname - thats ok. But what is the way to define a second or third domainname to the same web ?
I mean Not with the Forwarding-Feature.
I am missing in the DNS-Configuration a free CNAME Definition but cannot find a way to change the DNS to what i want.

I need for example:

www.domain1.net CNAME domain1.net
domain2.net CNAME domain1.net
www.domain2.net CNAME domain1.net