Select “Static IP address” from the drop-down menu.  Fill in your desired IP address and default gateway address.  The “Subnet mask” box will get filled in automatically when you fill in the IP address.  You won’t need to change the mask unless you’ve subnetted your network.  (If you’re a normal home user, you won’t have need to subnet.  If you’re in an office environment, your IT folk will tell you if you need to enter a modified mask.)

The “Local Zeroconf. . . ” option works just like the “Automatic configuration” option, except that it also allows you to immediately see and use any network-enabled resources on your local network.  (This includes network-enabled printers, file servers, and media servers.)

Ubuntu network, Static, ubuntu