Read through your camera's manual to understand the manual settings that let you adjust the brightness of the camera. By reading, you learn that brightening your picture allows more light into the lens.
Switch the settings of your camera from automatic to manual. This allows you to manipulate the settings to get brighter pictures.
Select a higher ISO setting (larger number) from your camera's main menu. A number that is too high makes the picture look grainy.
Mount your camera on a tripod for stability. Slow the camera's shutter speed to allow more light into the lens -- for example, from 1/100th to 1/20th of a second. A lower shutter speed might make the picture blurry, which is why you need stability.
Widen the aperture to let in more light into the lens. "F-stop" represents the aperture size -- the smaller the "f-stop," the wider the aperture.
Take pictures of an object and view the image. Adjust the settings until you get the desired brightness.