1
Move your cursor up to the top menu bar. Click "System", then "Settings" and finally, choose the option "Monitors". This window might pop up:

2
Choose your setting. The button besides "Resolution" hides a drop - down menu containing a bunch of different screen resolutions.

If you want to save power, choose the lowest resolution.
If you want the image to be as sharp as possible, you're good to go with the highest possible resolution.
If your own monitor allows a refreshing rate at 60 Hz, then let it be so. Otherwise, turn it down to 50.

3
Leave the "rotation" to be normal, and click "Apply" and then "Close" when you are finished.

Hope this helps.
Enjoy! - Nasty