three-point lighting system:
If you add extra light, follow the three-point system: be careful, if you don 't have safe lighting fixtures or you cannot work safely, stick to natural light. Using artificial lighting complicates matters, costs extra time and does not always produce better results!
Key light is the main light, and is used to highlight the subject. The light is placed on one side of the camera
so it highlights one of the subject's sides. Mostly, the key is placed at a 30–60° horizontal angle from the camera (0°) and at a height of about 30°; that seems natural as it mimics the sun.
What to use for this? As a key light you can use a string light source, for example a theatre spot light or any other spot light that you can put high enough alongside the camera. A desk light sometimes will serve this purpose well. Ideally speaking a key light can be adjusted so that it only throws the light where it is needed and nowhere else.
Fill light is a soft, broad light used to reduce contrast in your shot; it softens the shadows created by the key light.
How to set this up? The fill is either a light or a reflective screen that provides soft light; it is placed on the other side of the camera from the key light. The soft light is used to soften the shadows on the subject: it throws light on the subject where the key light does not reach. The fill light also provides a general light for the whole scene. Fill lights are normally large. You can make use of large windows as fill lights by simply putting your camera in front of the large window, facing away from it.
Back light is a light that illuminates the subject from the back, providing a glow of the subject's edges, such as an interviewee's head and shoulders. Please note that it is different from background light, which lights the background behind the subject.
What to use for this? For back lights, you can use similar lights as for the back lights: use lighting fixtures that you can control somewhat so that they don 't spill light everywhere.