There is a recipe to setting up your lights. Let me begin at the beginning. The first concept taught in photography class is the exposure triangle: ISO, aperture and shutter speed.
ISO has to do with the sensitivity of the digital sensor. You may remember back in the day buying 100 or 400 “speed” film. 100 was for bright, sunny days, and 400 was for shady or bright indoor situations. Same thing with digital. The lower the number, the crisper your image. The higher the number, more “noise” (graininess) gets introduced.
Aperture (f stop) has to do with depth of field. Do you want a blurry background or a crisp background? The higher the number (f/11, f/16 for example) the farther your depth of field goes, BUT the smaller your camera “pupil” is and less light is let in.
Shutter speed is kind of like an eyelid. The longer the shutter is open, more light is let in (1/60 = one sixtieth of a second, for example). With a slow blink, the eye is open longer and more light gets in, and with a quick blink (1/125, 1/250) the eye isn’t open very long and less light gets in.