F-numbers are the denominator of a fraction, so smaller numbers refer to larger aperture sizes. With kit lenses, the largest apertures are usually 3.5-5.6, depending on zoom. For low light, you need "faster" lenses with larger apertures (smaller F-numbers).

You should also set ISO to auto and forget about it

• If images are too dark and you have to brighten them in post, the result will be worse than if you'd let the camera use higher ISO in the first place.

• If you compensate for low light with longer shutter speeds, you'll get more blurry photos. Blurry, noise-free photos are pretty useless. Sharp photos with some noise are still useful.