A: It's been challenging, as every other month products seem to be on and off of Amazon. I'm not quite sure why. However, I found this blue light lamp and it is a suitable alternative to the one I originally recommended.
To answer your question, generally the light box should provide an exposure of 10,000 lux of light and emit as little of UV light as possible. You want to use that within the first hour of waking up in the morning for about 20 to 30 minutes, about 18 to 24 inches away from your face with your eyes open, but not looking directly at the light.
The light box is a fabulous thing, but if you have any exposure to natural light you could also use that. I'm not sure in what part of the world you live, but in places where now it's summertime or if you live in the Southern part of the United States, you might still be able to get exposure to outdoor lighting. That might actually work better than the blue light therapy.
White light can be helpful, but unfortunately not as effective as blue light. Blue light, and only eight lux of blue light per day, can be as helpful as 12,000 lux of white light. Therefore, generally I would look for a blue light therapy box if you can find one.