Witcher 3 with widescreen mode?

[Atton Rand]

I have a 15 inch 1024x768 VGA monitor (Benq FP531) . I played assassins creed unity with the black bars on top and bottom (aka letterbox) by turning Widescreen ON in settings. Is there a similar setting for Witcher 3 or do I have to change something in GPU settings? I have a GTX 960 2GB GPU.