Check out MiK$\rm{\TeX}$ or alternatives such as $\rm\TeX$ Live, or any of the others detailed at The $\rm\LaTeX$ Project. All the distributions include and support $\rm\TeX$ and $\rm\LaTeX$.
I do most of my work on Linux machines ($\rm\TeX$ Live or te$\rm\TeX$), but use Mac$\rm\TeX$ on my Mac.
I use MiK$\rm\TeX$ on Windows 10, and through the package manager you can install mhchem (and a zillion other packages). There is a document previewer called yap (Yet Another Previewer) that comes bundled with MiK$\rm\TeX$ which will allow you to preview your typeset documents, which you will create using an editor called $\rm\TeX$works. The workflow is typeset in $\rm\TeX$works, view using yap. You can then copy and paste the source code into the box here on Chem.SE.
The help documentation for MiK$\rm\TeX$ is quite extensive and the project is, like the others mentioned above, well-maintained.
Note that you will have to install several packages using the package manager in order to get mhchem to work. The following $\rm\LaTeX$ source, compiled with the pdf$\rm\LaTeX$ interpreter in $\rm\TeX$works, is an example of what you might want:
\documentclass[10pt, a4paper]{article}
\usepackage[version=4]{mhchem}
\begin{document}
$\ce{NaOH -> Na+ + OH-}$
\end{document}
which produces
$$\ce{NaOH -> Na+ + OH-}$$
in the pop-up window.