this might not be the exact steps as i dont want to break my eyefinity setup right now.
plug in the extra display. (it will most likely duplicate your laptop screen onto the monitor/tv)
right click on the desktop
click "screen resolution"
click on one of the blue squares(they represent your screens)
to the right of where it says "Multiple displays" tell it to "extend desktop to this display"
if the options arent there try a different square.