How do I install a monitor to my macbook pro?

Hi

I have a 2012 Macbook pro and I would like to connect it to a View Sonic monitor. I have purchased a belkin Mini Display Port to VGA Adaptor which seems to connect. However the screen does not work and my macbook pro does not appear to detect the monitor whenI look under System Preferences. Does anyone know if there is another step I need to complete? I rebooted my laptop and unplugged the power and chords in the monitor and reconnected after leaving oiut for 30 seconds however this did not change anything.

Any assistance will be greatly appreciated!