As a root user, you can add a declaration to the device in /etc/network/interfaces.
Open the file from a terminal with: sudo gedit /etc/network/interfaces – password tabernus
Add
auto <eth adaptor you are configuring>
allow-hotplug <eth adaptor as above>
iface <eth adaptor as above> inet static
address <IP ADDRESS you want>
netmask <NETMASK you want>