sudo vi /etc/network/interfaces

iface eth0 inet dhcp - remove "dhcp" change to static    
	address 192.168.xxx.xxx - IP of your Computer
	network 192.168.1.0
	netmask 255.255.255.0
	broadcast 192.168.xxx.255 
	gateway 192.168.xxx.xxx - Router
	dns-nameservers 192.168.xxx.xxx 8.8.8.8 - replace xxx with your router ip

Replace xxx with proper IP configuration for your network