You can run the RedHat network config command:
You can manually edit the file in /etc/sysconfig/network-scripts. File will be ifcfg-eth0 for eth0, ifcfg-eth1 for eth1 etc...
An example file from my RH AS 3 system:
ETHTOOL_OPTS="autoneg off speed 100 duplex full"
In the above:
The BOOTPROTO tells it to do either dhcp or static - you want static.
HWADDR should NOT be changed. This is the MAC address specific to your card.
ONBOOT=yes tells it start up at boot.
IPADDR is the static IP address.
NETMASK and GATEWAY should be whatever is appropriate to your network.
ETHTOOL_OPTS - Above turns off auto negotiation and hard sets the interface to speed 100 and full duplex. This is not required and may not work on some NICs. See ethtool man page for more detail. If it doesn't work then mii-tool likely does.
Don't forget to also update your /etc/hosts file with the IP.
P.S. The MAC, IPADDR and other things above were obfuscated so don't tell me the NETMASK isn't right.