How to use Clamshell (closed laptop) mode with a Macbook and external monitor.
- Make sure the external keyboard, mouse, power adapter, and external monitor are connected to your MacBook ,MacBook Air, or MacBook Pro.
- Make sure your Mac had POWER (this is important).
- Close the lid of your laptop.
- Keep the lid closed, press any key on the external keyboard to wake your MacBook/Pro from sleep.