Enabling the Secondary Monitor
To enable a monitor you must first have it plugged in on start up. The first step is to right click on your desktop and select the Properties selection.
Now click on the "Settings" tab.
Your monitor will appear grayed out. Select it by clicking on the monitor "box" and then checking the "Extend my Windows desktop onto this montitor" and then click the "Apply" button.
Your monitor should now blink on. The next thing I like to do is position the monitor in Windows where it actually sits on my desk. In my case, I actually have it on the right of my primary monitor. Click and drag the secondary monitor to the appropriate area. If you're like me and have different size monitors (plus it is rotated 90 degrees in portrait mode) you can use the arrow keys to more finely tune where your monitor resides in respect to it's height to the primary monitor. This will help visually as your mouse will more easily flow from one screen to the other.
That should do it.
Disabling the secondary monitor
If you need to remove the second monitor for any reason, go into the display properties first and disable the monitor. If you don't, your display properties might show up in the secondary monitor and you won't be able to see it.
Go back to the "Settings" tab
Click the monitor you wish to disable. In this case it's the secondary monitor. If you click on the "Identify" button, a big 1 or 2 will appear on the respective monitor.
Uncheck the "Extend my Windows desktop onto this montitor" and click the "Apply" button.
If everything looks good you can click the "OK" button and you're done. You can now disconnect the disabled monitor.