This is awesome. You could go get some fertilizer, just follow the directions so you don't overdo it. A fertilizer with high phosphorus us what you'll want to use at this stage. As for the light, it definitely needs it, but it seems to be doing great as it is. If you want to add light you'll need to make sure that you use a timer so that the lights turn on and off about when the sun rises and sets, and for 10 to 12 hours per day. It'll probably be safest to have lights on for 10 hours in the middle of the time when it's daylight. If the lights are on for longer the plant won't want to flower. A couple compact flourescent lights that are reddish, or listed as about 2700k should be great. Keep the plant watered but wait for the soil to dry out on the top before watering again, although it should still be somewhat moist if you stick your finger in the soil a bit. Good luck and keep us updated.