The dictionary (Webster) defines photography as "the art or process of producing images by the action of radiant energy and especially light on a sensitive surface".

This means that we create our images by capturing light (photons), reflected from our subjects, with some sort of detection device. That means we will not be able to capture anything in absolute darkness.
Landscape photographers usually rely on the sun as their source of light, but creating our own source of light at night is not a new concept. Painting with light simply means that you brought your own light source and that you choose what to light and what not.

On my last trip to Mono Lake, I thought that the bizarre shapes of the lake would lend themselves to this technique. After the sun set, I set up my camera on a tripod and chose an exposure of around 30 seconds, so I would have enough time to sweep as much of the landscape with my spotlight as I needed. I used a mid range aperture setting of around f-8 to start and adjusted the aperture accordingly after the first shot. You have to use manual settings, as the camera cannot evaluate the scene correctly with the spotlight. You need about 20s-30s to evenly paint a scene with a strong spot light.

I bought a 2.2 Million Candlepower light, before I went out to Mono Lake. I recommend at least 1 Million Candlepower for landscapes. The further your subject is away from you, the longer you need to paint it. Stand a few feet away from your camera and use a remote control or timer or another person to release the shutter. If you stand too close, your light beam might make nasty streaks across the frame, especially if you are shooting with a wide lens. Start painting shortly before releasing the shutter and keep painting until you hear the shutter again. Move your spotlight with an even pace across your subject.

If you light something that is farther away, you need to expose longer. If you double the distance, you need to increase the time by roughly four times to get the same brightness.

Painting with light drastically changes how a scene looks like (compare the two images at the top of the post).