There are a few actions you can take:
Expose to the right by either opening up the lens aperture or by using a slower shutter speed. An underexposed image later brightened on a computer will result in a lot of noise and other artefacts.
Determine your camera’s high ISO capability by conducting a simple test. Place your camera on a tripod and take the same photograph of a subject with dark areas, at various ISO starting at 100 all the way up by increment of full stops. Verify the progression in the amount of noise by enlarging each image on your computer screen.
