Hi Jeanne -- this might depend on what kind of seedlings you have growing... but for pretty much everything that I start under lights, veggies and flowers, I have the lights on for about 16 hours/day and keep them pretty close to the plants. That depends, again, on what kind of lights you have -- mine are just the "old-fashioned" shop lights, with T12 bulbs. (The newer, high-output bulbs don't need to be as close to the plants, from what I've read.)
