How can I get 2560X1080 resolution on my LG 29UM58-P monitor, connected to my 13" MacBook Pro? I have a MacBook Pro (Retina, 13"-inch, Early 2013) with 8Gb RAM and Intel HD Graphics 4000

I also have a 19" Polyview 16:9 monitor connected via Thunderbolt to VGA adaptor, which displays its native resolution of 1440x900. 

I recently purchased an LG 29UM58-P ultra wide monitor, which has a native selection of 2560x1080 at 21:9 aspect ratio, connected via my HDMI port. Unfortunately, all windows and text is stretched to fill the screen.

In System Preference --> Display --> Resolution --> I can choose from 1600x900, 1080p, 108i and 720p. I have selected 1080p at 60 Hertz. 

I've also downloaded the Onscreen Control app from LG's, but can't seem to access it in System Preferences even after selecting it in Security &amp; Privacy --> the Accessibility panel ??

How can I get my monitor to display its native resolution at the correct aspect ratio without stretching all the windows etc?

Many thanks in advance for your help! :)
According to MacTracker, your 13" 2013 MacBook Pro can support:


up to 1920 by 1080 pixels on HDMI;
up to 2560 by 1600 pixels on Thunderbolt.


So you need to swap the connectors used by each display.