Need help with keyboard backlight (Dell Inspiron 15 7559)

Hello, I'm having a small problem with my new Dell laptop.

I can't find the option where I could set my keyboard backlight to stay on constantly. It keeps falling asleep (turning off) after a short period of time. It is really annoying late in the evening as I always have to wake it up. Is there any way I could turn off the automatic sleep mode or atleast prolong it?

Thanks in advance :)