You may want to set a static IP and there are two easy ways to do so. 

The first way, you can use the GUI. go to the arrows in the top right, and right click or secondary click on this and then select ‘Wireless and Wired Network settings’. From there choose the interface, which is usually eth0 and fill in the IP address, router and DNS server you wish to use.

The second way is to edit a config file. Open a terminal from the bar and type in “nano /etc/dhcpcd.conf” then return. this will open the file in the nano editor within the terminal. Using the down arrow navigate to a commented out section with the example static IP. you’ll need to uncomment the interface line, static IP line, static routers line, and static domain name servers line. Then edit the address to what you need for your setup. If you’re only using IPv4 then remove the IPv6 DNS server. do a sudo reboot to apply. 

Once back up you can verify in two ways. 

The first way is to look in the GUI as before to see the details are now present. 

The second way is to again open a terminal and type “ip address show” to list the IP details for each interface.