Certified GKH Gardening Expert
You can set the time, anywhere, between 12 and 18 hours of light. 12 hours a day will save energy.
As far as how high to hang the light- That depends on what light source you choose. Generally, the light of your choice will have hanging instructions and you can adjust to the plants needs as you see fit. Unfortunately, this answer isn't straight forward.
Watering should occur as the soil dries, thoroughly, down to about 2 or 3 inches. Once it is dry down to that depth, you can water until it starts to drip out of the drainage holes. Make sure to discard all extra water from the saucer.
These articles will help: