You need to install a TeX distribution and select a LaTeX editor. You can download all this software for free.
Selecting a TeX Distribution
Before you can begin working with LaTeX, you need to first install a TeX distribution. This is a typesetting program that takes the LaTeX files and generates output based on the settings in the LaTeX files.
TeX distributions are available for Linux, Windows and MAC.
For Windows, you can use proTeXt which you can download at www.tug.org/protext/.
For MAC OS, you can use MacTeX, which can be downloaded at www.tug.org/mactex/.
Instructions for installing these programs are provided on the sites where they are available.
Selecting a LaTeX Editor
Using a simple text editor has its advantages. I can create LaTeX files in an editor such as NotePad++, Atom or even Eclipse and then compile the LaTeX file on the Command Line.
Plenty of LaTeX editors are available.
So, you can choose how you best want to work. For me, an editor that adds tags, closes tags correctly and has a menu selection for generating output works fine.