The settings file will be in left4dead2/UniversalFog/Settings.cfg
You need to have launched a map with the mod on at least once for it to appear.
If everything is Chinese, use something like Notepad++ and that should fix it.

The Settings are as follows:
Universal_FogColor = "0 0 0",
The universal fog color applied to all maps in RGB with a range of 0-255. To not change it in all maps simply set it to "NO" (quotations included)

Universal_FogStart = 300,
The universal fog start position in hammer units applied to all maps. To not change it in all maps simply set it to "NO" (quotations included)

Universal_FogEnd = 700,
The universal fog end position in hammer units applied to all maps. To not change it in all maps simply set it to "NO" (quotations included)

Universal_FogDensity = 1,
The universal fog density/opacity applied to all maps. To not change it in all maps simply set it to "NO" (quotations included)

////////////////
//MAP SPECIFIC
////////////////

To make map specific settings, copy the universal fog settings but replace "Universal" with the map filename of the map you want to apply it to.

So if I wanted to change the fog color on map 2 of Dead Center, I would add a line in the settings like this:
c1m2_streets_FogColor = "255 255 255",

To disable the universal fog settings from applying to specific maps, do the same as above but end it with _Disabled.

So if I wanted to disable fog changing on map 3 of Dead Center, I would add a line in the settings like this:
c1m3_mall_Disabled = 1,