Hello donna:
The original Mach3 manual, written for the most part by Art Fennerty, the man who wrote Mach2/3 is available on the NewFangled site.
Here is the link:
http://www.machsupport.com/wp-content/uploads/2013/02/Mach3Mill_Install_Config.pdfThis document covers every step of learning a CNC machine, in great detail. This document has been available for at least 10 years. There are other books dealing with CNC that go into detail regarding the developement of CNC programming and G-code. Look on Amazon for books authored by "Smids". His books are considered the best available for the inner workings of and explanation of G-code, and programming.
The NewFangled website has many other documents available. There are also many videos, many made by Art Fennerty.
Learning to make parts on a CNC machine is a lengthy process, with many levels of machine tools; simple stepping motors machines to high-speed AC Servo driven machines.
Building a small CNC stepper motor driven mill or engraving machine is not too difficult, but requires some basic knowledge of electrical wiring, soldering, and mechanical assembly. There are many, many YouTube videos made by people like yourself, who self-taught themselves, and built a CNC machine.
This whole process does require a lot of time, and patience.
The Mach3 forum site also has a section for FAQ, answering many basic questions.
John