Add Sunlight
During the winter, the sun sets earlier, is lower in the sky, and covered with clouds. It is important to make sure your houseplants are getting enough light during this time. If plants are leaning towards their light source, gradually rotate them every few days to help them straighten out. If plants have spindly new growth, move them closer to the sunlight.
What about Artificial Light?
Any fixture, floor, or desk lamp approx 1-3 feet away from your plant will suffice. CFL bulbs are a good alternative but LED bulbs can be more energy efficient and produce less heat to produce light during the darker days