Many digital cameras come equipped with flash compensation settings, and they do so for very good reason. The flash on your camera cannot exactly be controlled as to how much light is being emitted. Unless you have a hot shoe flash, you cannot even control the direction of the light. Because of this, the flash can make things look too bright in many situations. Then, sometimes, the flash will not be enough and the image will look dark. The flash compensation can be the answer.
Generally located in the menu of your camera, the flash compensation works quite simply. You can either change it for the plus or minus. If you change it for the plus, then it will make the picture lighter over all. Basically, this is giving your flash a boost for dark settings. If you change it for the minus, it will darken the picture overall, so it will be toning down the power of the flash.
To locate the flash compensation on your camera, either look it up in the manual, or look on the back screen of the device. Often, it is indicated with a lightning bolt with a +/- beside it. Be careful not to go overboard with the flash compensation or you could end up with way too bright or way too dark images.