How would I turn down the ambient lighting of a map? I want to make a nighttime map, but when I play in game, everything is still bright. Where can I change this?

Under the Lighting tab on the right side, find the top and bottom ambient colors. Mess around with those. Setting all of the numbers lower would make your world darker.

Thanks so much, now I just have to play around with it to get the right settings. This can be locked.

Have a look at the lighting doc that came with the modtools as well, very helpful.