[Typo3] how to access other sites than the top site?

[Bing Du]

Multiple sites were created in one database.  I noticed the URL (in my 
particular case http://www.my.edu/IT) by default points to the top site 
in the page tree (Dept A's web site).  Since all is in test phase now. 
No domain names were registered for each site.  So the question is how 
can I access Dept B's web site?  Does it have its own subdirectory?

Dept A's web site
   About
   Schedule
   People

Dept B's web site
   About
   Schedule
   People

Thanks in advance for any help,

Bing