Edit the following file:/etc/network/interfaces

and adjust it to your needs (in this example setup I will use the IP address 192.168.1.101)

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface

auto lo
iface lo inet loopback

# This is a list of hotpluggable network interfaces
# They will be activated automatically by the hotplug subsystem.

mapping hotplug
script grep
map eth0

# The primary network interface

auto eth0
iface eth0 inet static
address 192.168.1.101
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.1