See this tab in with the icon of the two plugs? Click on it and launch the Device Connector.
To begin press the Home Button on the Magic Remote then navigate to the right until the all apps are reappears.
It might be surprised what you can connect: everything from a smartphone or tablet, your PC and of course the Blu-ray Player, Home Theater System or sound bar. Part of what makes LG Smart TV with webOS so smart is the way it connects other devices.