How to change aperture, shutter speed, ISO, and exposure on a Nikon D40?

I'm a new photography student and just got my first DSLR camera. I already finished a semester of Digital Photography class, and we learned nothing about any of the things I mentioned in my question. But those seem to be the 4 basic principles of photography from what I have been reading online. I can't figure out how to change them on my camera at all. Could someone please tell me step by step (including what buttons to press and everything) for each thing? I'm so confused. I mess around with my camera and think I'm changing them, but my pictures never look any different. Please also explain what each one of these things does.

Download the instructions for your camera from the Nikon website and start reading.

This link will help you to balance ISO, Shutter Speed and Lens Aperture by using the cameras lightmeter

http://camerasim.com/apps/camera-simulator/

Read the user manual - it will tell you how to change all the settings on your camera.

If you lost your user manual, you can download it here: https://support.nikonusa.com/...a_id/14157

Then read this: Understanding Exposure http://www.cambridgeincolour.com/...posure.htm

After reading the Owner's Manual for your camera read this:
http://digital-photography-school.com/learning-exposure-in-digital-photography

How can you do a 'digital photography' class and NOT learn about the very basics of exposure!

Firstly - 'exposure' is not a setting you change - it's what you get when you change the settings that control it - ISO, aperture & shutter speed.

The only way to control all 3 independently (ie without changing one, automatically changing another) is to be in M (manual) exposure mode. Turn the top dial until the M lines up with the mark.

ISO should be kept low as often as you can (100-200).

If freezing motion (or blurring it) is your goal, then next you set an appropriate shutter speed.

Finally, set the aperture, whilst looknig at the light meter in the viewfinder (looks like this I--I--0--I--I ) - aim to get the light meter marker somewhere around the middle (ie zero'd).

If controlling depth of field is your goal, then set aperture first (wide aperture, low f number for a shallow depth of field; narrow aperture, high f number for a deep depth of field).

Then finally set shutter speed tp adjust light meter marker as above.