How to make sunlight (directional light)

Hello,

I am creating a larger terrain using an instance. I have no problem here. Now I would like to make sunlight (directional light). I tried to change the pixel shader (terrain material). Unfortunately with poor results. Please help.

Another question. How to combine data for directional light (direction, power) and weather data (rain power, snow power). Will they be needed to create the appropriate effects?