The usual npm commands in the project root:
npm install
(which should only need to be done once, after that everything is installed )npm start
will start the server so you can access the site via browser
There are several files you don't need to be concerned with. These are the ones you should be
/index.html
is the html served when you start the app/js
is the directory with the JavaScript files loaded by index.html/css
is the directory with the CSS files loaded by index.html