How to Close a MacBook and See It on an Attached Display
To use an external display with your MacBook, you will need to connect the monitor to the Mini DisplayPort on your laptop. Some newer MacBooks allow you to connect an external monitor using the built-in HDMI port. You may have to use an adapter with the Mini DisplayPort, depending on the type of connection you use with the external monitor. Once you connect the external monitor, you can choose to use the external display as an additional monitor, or close the MacBook's lid and mirror the display.
1 Connect a Keyboard, Mouse and Monitor
Since you will not have access to the internal keyboard and trackpad when the MacBook is closed, you will need to connect an external keyboard and mouse via USB or Bluetooth. Ensure that the external display is also connected to the HDMI or Mini DisplayPort on your MacBook. The MacBook's power adapter must also be connected and plugged in.
2 Close the MacBook's Lid
After you have connected the keyboard, mouse, power adapter and external display, close the lid of your MacBook. In OS X Lion and above, the external display will briefly show a blue screen and then your desktop. In earlier versions of OS X, you have to wake the computer by pressing any button on the external keyboard or mouse before the desktop will appear on the external monitor.