run ifconfig to find the name of your Interface.  Normally these would be eth0, eth1 etc but in my Virtual Environment they are different

cd /etc/network
sudo nano interfaces

Make all changes required, including:

• Change from DHCP to Static
• Add Address, Netmask and Gateway

Write out file using Control + O, Overwrite File and Control-X (to exit)

Restart the network interfaces by:

sudo ifdown ens33 && sudo ifup ens33 (substituting ens33 with your interface)