The easiest way to experiment with your camera's exposure controls is to set it down on a table, put the camera in Manual exposure mode, and watch the LCD to see how adjusting the shutter speed and aperture changes the brightness of the image. Start, for example, with a shutter speed of 1/10 second and an aperture of f/4. You might see something like the dim image on the left.
Now spin the shutter-speed dial. As you slow down the shutter speed (lengthening the time the shutter stays open), the image becomes brighter and overexposed, as you can see here on the right. Speed up the shutter speed again, and it gets darker and underexposed.