You need to find a steady surface to place the camera when you take the shots in low light situations, use the max. aperture possible and max ISO tolerable (w.r.t. graininess of the pic).
If the subject is not moving, then no issue, just click the photo while the camera is resting on the surface (or use the auto timer so that you are not touching the camera and it is 100% steady).
If the subject is moving, you will need to use the inbuilt flash. Normally this will freeze motion at the cost of a harsh looking photo. You can dull the flash a little by covering it using a tissue paper/white cloth to diffuse the light, you can also use a white card to angle the light to the roof.
Of course you always have the option of buying faster lenses (the 50mm 1.8 as suggested by sabby), which will help you to some degree, but for low light a tripod/monopod/bean bag is almost compulsory. You could also splurge on external flashes that have inbuilt redirection/diffusion options. But all these options depend on how much you are willing to spend