Is a lot to take in with light, just know pure light is uniform plus distance and intensity (in daz you can control that), like a white piece of paper (that is the light, is all light) and on it you start add objects and by doing so you create shades and those shades create the scene, it gives it form, shape and since you work in daz everything is already 3D.
White reflects, black absorbs, material fabric density, light can pass through or not and creates those rays, like those window lights is that opening in the wall that creates the spread of light into the room and is those particles of dust or smoke, etc that creates the rays, cause otherwise light is uniform and equally spread.
As for shadows, there's the shadow on the object, the shadow that falls from object, and the shadow between the light and dark shadow (the shading in painting, highlights/midtones/shadows in photography)
So is not the light as much to focus on but what you add to the scene and manipulate the light to get the results you want.
And i will try to reinstall when get the time, is not as much the files that go through install manager but all the others, feels like modding skyrim all over again.