Having a firm grasp of these individual pieces and how they can alter an image is crucial to being able to get the outcome that you desire. The best advice that I can give is to set your camera in manual mode and go take a ton of shots. It may even be beneficial to take notes of the settings when you are doing this so you can compare the settings to the results. Digital cameras have a built in light meter so you know when then camera says the image is exposed properly. The meter will show 0. As the meter slides to the left into the negative the image becomes under exposed (darker), as it slides right to the positive side it becomes overexposed (lighter). The issue with this meter is that sometimes lenses behave differently and may tend to slightly over or under expose an image. The other issue with the meter is that you may not always want a “perfectly” exposed shot. Sometimes when trying to get a specific look the image needs to be under or over exposed.
Once you have a firm grasp of how all these things work together from experimenting you can venture into the semi automatic modes of the camera. Aperture priority mode will allow you to set the aperture and ISO (unless using auto ISO) while the camera takes care of the shutter speed. You can still alter this a bit as the camera will allow you to adjust how it meters the light. Take a test shot, if it’s not exposed the way you want you can slide the exposure compensation to one side or the other to get the desired effect. Shutter priority mode allows you to set the shutter speed and the camera takes care of the aperture. I’ll discuss these modes in depth at a later date but this should be sufficient to get you started.
As always, snap lots of photos, have fun and don’t be afraid to experiment, especially if you’re using digital. There is essentially no cost. Of course in most cases the shutter is mechanical meaning that at some point it will fail but despite hearing a lot of photographers worry about this it is absolutely not something that I ever concern myself with. I bought the camera to use it and photograph what I desire, not to let it sit and worry about the shutter dying.