The lightning Bolt is a symbol for the flash. I do not know the operation of your particular camera, but the symbol in the viewfinder could mean you need to use the flash, or that the flash will fire. If you do not want the flash to fire but still want to take pictures in low light, you need a wide aperture lens and/or a high ISO setting.
Aperture is how big an opening the lens can make. The aperture on your camera varies from f/3.4 to f/5.7. Lower numbers is better; a better camera lens would have an aperture of f/1.8 or f/2.0.
ISO is the setting for the sensitivity of the digital imaging sensor. Your camera has a maximum ISO of 1600. That would allow you to take pictures in low light, but the picture quality will be very grainy or noisy. If you only look at the photos in a small size, the grainy noisiness may be acceptable to you. A better camera would allow you to use ISO 1600 or even higher with much less noise or graininess.