ok, I'll explain.
Now, When you have ZHLTools, then just replace the 4 file, found in your '...programs/Valve Hammer Editor/tools/' (files include 'hlbsp.exe', 'hlcsg.exe', 'hlrad.exe', and 'hlvis.exe') Since you seem to have used the lights.rad file before, it should also be found in the tools directory.
if you have a custom rad file for a certain map, it would be as follows:
'dm1.map' for example, would have 'dm1.rad' Or you can just use the 'lights.rad' for all your maps.
Now, the lights.rad file if opened in notepad shows all the color, and brightness levels of the textures.
So yea, first, replace all the ZHLTs in the hammers tools/directory..
Hammer automatically includes the light.rad file when it compiles.
If your not sure how the light.rad file works, it is as follows:
1.Name of the texture you want to admit light
2. Red color amount
3. Green color amount
4. Blue Color amount
5. Brightness
So in this case where I have a white light texture called '~light1bright'
then in the lights.rad file, once opened in notepad, you will write:
~light1bright 200 200 200 1000
Since we want a white light, all rgb values are high, and the same.. 1000 is the brightness of the light..
So that should get you started.. anymore questions, and I'll be glad to help.