Blooming plants as they are now in flower? If so, what lights were the plants under up to now? Or, were they growing outside? Or is this another light to be used along with whatever you already have?
If the light was bought from a grow store the staff there should have an idea. If the light was bought from a hardware store then who knows. But, I think starting off at about 18 inches between the light and the tops of the plant would be OK. Then adjust as needed if signs show on the plant.