Answer: If you really want to learn the basics of gardening, Arizona State University Cooperative Extension offers Master Gardener training. It is a thorough training in all things garden related. If you want to learn on your own, you can read the training manual (or download it, but it is several hundred pages!). The website address is: http://ag.arizona.edu/pubs/garden/mg/index.html
As for the mushrooms growing in your yard, they are growing there because there is some decaying organic matter beneath the soil. This can be construction debris, decomposing tree or shrub roots, or even bark mulch. Whatever is under the soil surface is what is encouraging the mushrooms to grow. I'd dig down directly beneath the mushrooms to see if you can determine just what is feeding them. If you find dead roots, old wood, etc., remove it and you won't have any more mushroom problems.
Best wishes with your new garden!
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