I decided to make simple tutorial about it.
So there are few easy steps.
1: At first of all check if file named lights.rad exists in your game folder.
To do so open main folder where are all folders with materials, models, cfg etc are.
Example: C:\Program Files (x86)\Steam\steamapps\YOUR_STEAM\half-life 2 episode two\ep2
If you don’t have such file, create one using notepad.
If you have it, open it.
2:Now search for texture using hammer texture browser.
I’ll use one of my textures.
As you can see, selected texture is ‘neths/neths_area1’ and this is what we are going to use so copy path of your texture.
3:Now when we have texture and lights.rad file, we are going to add line about this texture to it.
Paste path of your texture with color and brightness amount.
Example: neths/neths_area1 255 255 255 400