Summarize:

You can use an Ethernet cable to connect your TV to your router. Plug one end of the Ethernet cable into your router, and the other one into the port on the back of your smart TV. Open your smart TV's menu from your remote, and navigate to your network settings. This option may also have a different name like Wireless Settings or Internet Connection. Once this option is enabled and your TV is connected to your router, you should immediately connect to the internet.
Find the Ethernet port on the back of your TV. Connect an Ethernet cable from your router to your TV. Go to your smart TV's Network Settings menu. Select the option to enable wired internet connection.