Lighting is an essential component in the growth process of your aquarium plants. Without light, Your plants would not be able to to go through the important steps of photosynthesis. Without light, you'd have dead plants.
Most fish tanks come with adequate lighting for many aquarium plants. Some plants however, need a higher spectrum of lighting than the stock lighting can provide. You should consult the information for each specific plant you put into your tank to determine if you have the proper lighting needed.
Remember to maintain the lights in your fish tank as well. Periodically clean the tubes with a damp paper towel, or soft cloth. Make sure you do this when the lights are cool. Clean any debris off of enclosures that may surround your lighting system. Be sure to keep any electrical cords away from water whenever you're setting up or maintaining the lights of your aquarium.
Avoid setting your fish tank in naturally sunny spots, as this tends to promote algae growth. It's easier maintaining the time your lights are on in the fish tank, which gives your plants good growth, without creating excessive algae.
Get yourself an automatic timer to run your aquarium's lighting system. This way you won't have to worry about turning lights on and off. You're aquarium will run on an even schedule. Your fish will be happy, and so will the live plants in your aquarium.