LCD Backlight voltage requirement
Nothing changes. Calculate the resistor as normal (Vin- Vf) / If. The leds were chosen to match each other, and even if they are in parallel with a single resistor it is okay if you pay attention to the specs.

As it says, the remark is the the leds are in parallel, and they still give a 25 mA max current, so that's the maximum you want, not 4 x 25 mA.