Open Display Settings in Personalize or Control Panel to change settings. Don't use Presentation Mode (win key+P.) That is for a projector. Instead choose external monitor. There should be an F key in the top row to select external monitor. Check your manual. Read--
http://windows.microsoft.com/en-us/windows-8/how-connect-multiple-monitors
Your laptop screen is the main screen. The external monitor duplicates it, not the other way around.
Try shutting down the computer and restarting to clear the settings. Unplug the external monitor first.