It may seem a bit tricky, comparing to good-old-way method, when you include libs from CDNs and add some custom JSs & CSSs to doc's head.
But, I promise, you'll fall in love with npm-way when you get used to it ^-)
You must first ensure that Node.js and NPM are installed on your machine.Download and install version for your system.
When you're good with node & npm, the only remaining step is to install theme's package dependencies. You'll find a package.json file in the root of your directory structure. The default package.json file includes everything you need to get started.
To install dependencies open system command line, cd to project's dir & run:
Check theme's README.md