multi urls in a wpmu install.

I have successfully created a network and have 3 sites - the primary and 2 others. I have followed all directions and can see and edit both all, but when i go to a different computer and enter the url for one of the 2 "extra" sites, it redirects to the home page for my hosting site. i'm not a developer, but i know how to read a manual.. just not sure which to turn to now