The commands to configure a network interface is 'ifconfig'. You give an interace an IP using
ifconfig eth0 192.168.1.1
where eth0 is interface (first NIC) and 192.168.1.1 is IP, secnd NIC is eth1.
To see current settings run 'ifconfig' or 'ifconfig interface'.
Then there's 'route'. It sets routing table. Without parameters it also prints it to you. The command you'll probably need to use is
route add default gw IPaddress
route add default interface
They're both to set default gateway - the place all packates that doen't fit the rules go (usually it means the outside world). First one uses IP (you have a machine that provides Internet access), second one - interface (the machine you're running the command on provides Internat access).