Do you mean after RH9 starts, you are sitting at an X login screen, blue backround, RH in corner, with a box in the middle asking for a username, then when you enter, next a password?
If that is the case, enter root for username, then the root password you entered during install. You should then go into System Settings, Users and Groups, and set up another username and password to use for daily work. Root gives you tons of access, and therefore the ability to make lots of mistakes.
Hope this helps.