# Log in as root or su to root then nano /etc/network/interfaces
# Should look like this:
source /etc/network/interfaces.d/*
# The loopback network interface auto lo iface lo inet loopback
# The primary network interface allow-hotplug eth0 iface eth0 inet dhcp
And change it to:
# The primary network interface allow-hotplug eth0 iface eth0 inet static address 192.168.1.202 netmask 255.255.255.0 gateway 192.0.1.1
when done: service networking restart if the interface fails type: ifup eth0