The simple answer to how much light you should be giving your Venus flytrap is as much as you can! Venus flytraps are sun lovers. They are green for a reason: Most of the energy Venus flytraps generate for growing is created through photosynthesis.
As you have or will learn in your first biology course, light is the key component for photosynthesis. Since they live in nutrient-poor soil, Venus flytraps need to photosynthesize in order to get energy. What they can’t get through the sun and their roots, they make up for by trapping insects. However, a Venus flytrap can live forever without ever trapping a single insect as long as it is given plenty of sunlight.
Most growers agree that in order for a Venus flytrap to be really healthy, it needs a minimum of 4 hours of direct sunlight every day. We give ours about 8 hours of direct sunlight. If you choose to grow your plant indoors, this is going to be difficult to achieve.
Also, if grown indoors, your Venus flytrap won’t have the opportunity to catch as many insects as it would growing outside. Furthermore, the chance of mold starting in the soil is much higher if the plant is grown indoors. For these reasons, it is best to grow your plant outside.
Growing plants indoors or in a terrarium is not recommended, especially for the novice grower. If you grow your plant indoors, it should be placed on the sunniest windowsill in the house. And even then, it likely won’t be as healthy or have as good of coloration as it would growing outdoors.
If you choose to attempt to grow your Venus flytrap in a terrarium, you should use cool white fluorescent or LED bulbs. These provide the correct wavelength for growth and keep the heat down so your plant doesn’t cook. The bulbs should be a maximum distance of 6 inches away from your Venus flytrap.
I’ve had moderate success growing plants in a terrarium under artificial lights, but I only keep them in the terrarium for a month or two at a time, and then I move them outside.
