Connect an Ethernet cord to the port on the back of your computer as shown. Connect the other end of the ethernet cord to your router or modem depending on what you are using. You could also have a fiber connection.
Your computer should automatically establish a connection. If it doesn't, try restarting your computer.
This tutorial shows you how to check your Local Area Connection properties to make sure they are set correctly for an internet connection. This walks throught the steps on Windows 7, but Windows 8 & 10 should be very similar.
Click on the arrows to progress through the tutorial. You can click the image to see a larger version.
1. Go to the Start Menu on the lower left and click Control Panel. You may have to search for "Control Panel" in the search bar here in Windows 10.
2. Click Network and Internet.
3. Click Network and Sharing Center.
4. Click "Change adapter settings" on the left.
4. Right-Click on Local Area Connection and click Properties. If the Local Area Connection has a red X make sure there is an ethernet cable connected to your computer.
4. Select Internet Protocol Version 4 and then click Properties.
4. Make sure "Obtain an IP address automatically" and "Obtain DNS server address automatically" are selected as shown.
If it is then your computer is properly setup for an Ethernet connection. If you still can't get online double check your router or modem or contact tech support.