The beauty of PostCSS plugins is that most (if not all) can be installed using the same method as PostCSS itself, we can use the package manager of Node.js to handle the process.
We'll start with postcss-css-variables, which we will use to handle variable support; the source for this plugin is available from https://github.com/MadLittleMods/postcss-css-variables. Let's get it installed:
npm install --save-dev postcss-css-variables

At this point, Node will have also added an entry to the package.json file for the new plugin. Perfect—we can now put it to good use and switch to using the plugin in place of using SASS. Let's take a look at how to achieve this, as part of the upcoming exercise.