You can try following the RH
Cluster manual on the RH website if you also have the Cluster Suite. If not here is a
How To for CentOS. You should be able to follow it without getting lost. Good luck and post if you have trouble or get it working.
CentOS is the same source as RedHat but free and has the propriety RH software (i.e Cluster Suite) removed.
NappyT