I'm still new to linux myself, so someone please correct me if I am wrong.
When you installed the OS on the machine it should have requested a password for root. If you used a kickstart file it may have been defined there, and would not have prompted. Once you get logged on as root it's cheese from there.
useradd is the command you would be using (unless you are a GUI person), I'm not very familiar with specifics so checking the man page would be the best bet.[/u]