manage domains

[happylorii]

Hi,
This is a newbie question.
How do I create space for different domains?
I installed Joomla in one domain. When I ftp into another domain, I see the Joomla files from the 1st domain. I beleive I missed an important step when setting up the domains. Can someone please help me or point me to the manual. (Plesk was installed by my hosting co. I have virtual hosting...if that helps at all)
Thanks!