Black macbook with external monitor

Hi, I recently purchased a 21.5 inch monitor with a resolution of 1920 x 1080 and I am trying to use it as my main screen for my black macbook (mid 2008, 2.4 ghz, x3100, 250 gb hd). What I want to do is basically make my macbook a desktop when I am using this screen. The problem is I do not know how to use the macbook in clamshell mode with this screen. Every time I close my macbook and wake it up with my mouse or keyboard, the screen on the external shows the desktop in 1920 x 1080 but then the screen on the external goes black and does come back on.

I am able to use the screen as an extended desktop in 1920 x 1080 but not as the main screen itself. Also just for note, I am not trying to mirror the displays, just want the external to be the only one on at a resolution of 1920 x 1080. And it is connected through a dvi cable.

Thank you

 

NVM, I found a pretty easy fix, attach power cable to macbook, doh!

 

also.. when you are looking at the display setup, if you grab the white top bar in the picture of the display, and drag it from the built in screen to the external monitor, it'll make the external monitor the primary monitor.