Open the "display settings" in your computer and activate output to the TV screen. You can either mirror content of your computer on the TV or extend the display just like a dual monitor screen.
Pick up your TV remote and switch to "External Inputs" from the menu. You will need to change the default "Video 1" to a different selection which may be "HDMI 1" or "Video 2" depending on how you have made the connection.
Important: Make sure you connect the cable to the TV before turning on the computer as sometimes it may fail to recognize external display.