Cannot adjust horizontal and vertical screen sizes

[Guest]

When trying to change my screen vertical and horizontal sizing on my monitor, LG 23EA63V, whilst using HDMI in the settings it says 'Cannot be used. Available in D-SUB signal only.' 

 

The picture is quite a bit more blurry than when using DVI (Dual Link) as well, nothing i can do in my monitor setting either... Any ideas? 

[Goowpea]

Try to do this by adjusting your screen size using software included with GPU. AMD Catalyst Center has this options I believe (I'm using VGA monitor s i can't be sure) Nvidia should have similar options to in their GeForce go experience or some sort of Nvidia Control Panel.