This part is simple: you need LUX (units of measurement of light level), so look it up for plants you want to grow. It is always a good idea to collect few numbers, from different sources, and to cut off outliners. But... How to measure LUXes?
Well, if you use Android phone, just visit Google Play and get Lux Light Meter Pro. It is free and perfect.
If you use Apple, you are on your own; I was told that these guys charge for everything, including viruses.
As you can easily find out, the light level depends on the distance to the light source (inversely proportional to the square of the distance). In our home garden, plants grow up to the light and illumination of upper leaves can be degree of magnitude higher than of the lower ones. It is a common practice to cut plants to prevent them to reach the lamp. Or - if there is space - you can move the lamp up.
Speaking of the lamp: how to we hang it?
Very simple: the stillage has holes and the panel is shipped with cables. I use two shelves (means 60x120x100), so one shelf takes two panels, serving 60x60 square centimeters each. Unfortunately, cables are not long enough, so here are home made extenders:
By the way, panels can be equipped with brightness regulators as well as with IR/UV diodes. See, in natural environment, plant can receive information about events that happen around it, based both on total light level and on spectral characteristics of it.
Particularly, when the plant "sees" the UV light, it means that it is "under the sky" now and nothing covers it. So the plant stops growing (no need anymore) and florishing begins.