EFV

A camera works with something that is called Exposure Value (EV). That exposure value determines the correct combination of shutter speed and aperture, at a certain sensitivity (ISO), for a good exposure. This value is a constant, meaning that whatever combination of the two, always make up for the same number. So small aperture needs long shutter speed; large aperture needs shorter shutter speed. Of course there is a limit to your apertures. If it gets too dark, it needs the largest aperture, but to make the EV it needs shutter speeds that you cannot hand hold (like 1 sec.).

P-mode determines the combination itself, and sets its possibilities according to the available light (intensity of the light from the scene). The S-mode, you control the shutter speed, and the cam will try to match it with the correct aperture (giving the correct EV, remember?). The A-mode will try to match it with the correct shutter speed (again, giving the correct EV). Manual, you have to determine the combination itself, with the help of the exposure meter of the cam.

In this case you should have either used a flashgun with high guide number or moved closer to your subject. If you have to keep a fair amount of distance, working with flash becomes eminent. But don't expect the average flashgun to perform beyond approximately 75 feet.

Practice the aperture priority.

Use about f/5 - f/6. Use ISO 200.

Practice to change white balance often from fine to cloudy, to fluorescent to incandescent.

Use AF area mode: Manual option and use the Spot Metering.

Practice changing Matrix, Center Weighted, and Spot Metering.

The Center Weighted is often better than the Matrix.