Did you register your Red Hat server to the RHN network? What yum repositories are configured? Can you post the contents of the files in /etc/yum.repos.d? Do you have network connectivity, no firewall blocking, ...? By the way, Red Hat is not free, so I assume you bought a license. This gives you the right to support from Red Hat, so you could put your money to work and call them. If you didn't pay for a license then I suggest you look at free alternatives like CentOS for example.