Open the action center. It's represented by the speech bubble icon in the lower right corner of the screen and then click “Connect” (or use Windows logo key + K on the keyboard)
Select the receiving device. You may have to wait a minute or longer for the devices to pair. It may also fail and you'll need to close the connect windows and try again.
Type in the room code displayed on the TV and click “Connect”.
When finished, type Windows logo key + K and click “Disconnect”.