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Not all ASUS notebook models support backlit keyboard, so you may want to confirm with your store or
local ASUS support about this if necessary since the R701series is not sold in my region and I'm not as familiar with it.
Anyway, for the 'G' series gaming notebooks that support backlit keyboard, you will usually see symbols on the 'F3' and 'F4' keys and can brighten the keyboard backlight in Windows by pressing Fn+F4 a few times.
Also, if it's supported and working, the keyboard backlight will flash momentarily after you power on the unit before you get into windows, so that can give you an idea if it's supported and working at the hardware level.