You have to locate and break the power boxes. They are electrical boxes on the walls with green lights on them.

i mean in the map editor. i have the map made with destructible light sources but even without lights units are exposed but outside they are hided.

So I tried removing the roofs and now my units are hidden at night but the lights i set don't expose them they just stay hidden.

You can disable both individual light sources (so the targeting order should be like this: fusebox -> trigger -> light) or whole buildings (by targeting a roof entity, so fusebox -> trigger -> roof). You don't need to use breakable lights for this to work, just use regular ones.
Now, for buildings, you usually want to target roofs, because this way you'll get the NV filter for the building once lightning is no more, and all lights inside will be disabled automatically (so no need to target them all manually, just a roof and your work is done).
For any exterior lights (spotlights, street lamps, etc.) you want to target light sources. Important thing to note is that your light source CAN NOT be set to "shadow", it won't reveal your operators, it's a technical limitation. Light source must be set to either "none" or "box". Otherwise you'll be able to move in a lit area and game will still consider you to be in the darkness.
For getting rid of any FX effects (anything from objects/lights category), you also need to use DamageArea entity, with radius set to 0 and damage type set to "delete". For this the expected targetting is: fusebox -> trigger -> damagearea -> light_warm (or anything you want to delete once fusebox is used).
Map lightning, which is set with "Light Directional" and "Light Ambiental" entites that appear when making a new map, doesn't affect night concealment at all. It's just for visual purposes. Although make sure you keep their values reasonable, so your map isn't too bright (if so, with NV filter it's not eye friendly) and too dark either (so your interiors are not pitch black once lights are disabled).
Hopefully it's enough for you to start with, let me know if you have any further questions.

ok well that explains a lot but what if I want to keep the interiors dark inside except for lights that I add. basically im making an cave map where the only light i want inside is the lights I place so operators can stay hidden except in areas with placed lights. When i changed the ambient indoor light down to .50 they where still exposed.

Are you sure you set your map to be a night scenario? There's a checkbox in "map settings", that should be enough for it to work. If it's set properly you'll get a night vision (green) filter on screen. If there are no light sources on your map then whole should be considered dark. And again, ambient lightning doesn't matter in this case, it can even be set to something ridiculously big but if mission is set to be a night one, it will still limit humans' sight, despite it's visually not.

yes i had set it to night but as soon as my units enter under the roof I get the exposed icon even before i placed lights.

Ahhh I got this now. I had to check it twice. So basically roofed area always reveals your operators and that's also the reason we have to remove it when using a fusebox. It means you can't have a roof and be concealed at the same time, sorry. For now the solution would be not using the roof for your cave at all. Sorry for inconvenience.

Ok got it. I was able to fix the lights exposing units so thanks for the helps