Well, the obvious answer is buy some sutido lights, but I'm not sure if that is the answer you are looking for.
I'm not sure how much you know about lighting, so pardon me if you already know all of this, but the amount of light you get from the sun when you are outdoors is far more than you would get from any normal indoor lights. It isn't always obvious how much brighter it is outside because our pupils adjust based on the light intensity. When you go outside it might only seem like it is 2x as bright, when in reality it could more than 10x as bright. Which means to get good pictures indoors, you need very bright lights.
I don't know if you are talking about taking proper photographs or just snap shots of your friends, and I don't know if your problem is that your pictures are underexposed (or blurry because the camera has adjusted the shutter speed to increase exposure), or if the problem is that lighting just isn't giving you the look you want. So I can't necessairly tell you how to solve the problem. (But I'll give it a try anyway)
If the problem is due to being underexposed, then you need to determine what kind of lighting levels you have. You could always get a proper light meter, but your in-camera meter should give you a pretty good idea of the lighting conditions on your subject.
As far as how the aperture relates to the light levels; the larger the aperture (smaller f-stop) the more light comes in. But the aperture also affects the depth of field, so adjusting the aperture isn't always suitable for your situation.
A slower shutter speed would also get you more light, but there are limits to how slow you would want to go unless you are taking pictures of still life using a tripod.
You can also use different ISO settings, but higher ISOs can lead to more grainy pictures.
If the problem with your lighting is that it just doesn't look very natural, it could be because you are using a basic camera flash, which is a very hard light. You could try using a flash deflector (there are some cheap ways to make a home-made version), which would give you better lighting that isn't so harsh.
Some other people might have some better suggestions, although knowing exactly what your problem is would help. But as I said at the start of this post, if you are trying to do proper photography then the best solution (though not always the cheapest) is to get some good studio lights. If you are just trying to take some snap shots, and you don't want to spend too much money, then there isn't that much you can do other than using a flash, but you need to learn to use a flash properly to get good results.