In parent Interface you need to select the Ethernet adapter name. It should be available as a drop down choice.
If you do not know it, type
in the terminal.
Leave service blank. Specify your username/password in respective boxes, exactly as provided by the ISP.
Go to General Tab and check 'Automatically connect to this network when it's available'.
Save the settings and it should connect if everything goes well.
Note - If your ISP deploys MAC id authentication and earlier you were using Router to connect, then unless you register the MAC id of your Ubuntu PC Ethernet card, you may not get internet access.
I assume you are on DHCP i.e. ISP gives you a Dynamic IP and you have not subscribed to any services like Static/Fixed IP etc, then no changes in IPv4 tab are needed. Leave it as DHCP default.