Problem with Dell S2340L 23 inch Monitor and MacBook Pro

How can I get the full resolution of this monitor? The resolution of the monitor can go up to 1920 x 1080. In System Preferences the highest it lets me go is 1280 x 1024. It's set to "Scaled" instead of "Default for display". I have it connected to my Mac with a Mini DisplayPort to VGA adapter.

My specs -

Dell S2340L 23 inch Monitor

13 inch MacBook Pro (2.5 GHz Late 2012 Retina)

Intel HD Graphics 4000 1536 MB

Mac OS X 10.11.1