This is HTML template. To getting started you need only Browser to run HTML files. Better upload files to web server and run the site there.
If template is opened from local file system, some functions and features may not work. For example functions, that required PHP – Instagram, Twitter, Contact Form.
To customize template you can edit CSS and HTML files. Also if you are developer, there are available source files SCSS and JS (required ES6 transpiller). All used plugins added from Bower.
For each pages available blank CSS file for your customizations. See it here –
Also, note that all features described in template html files and not in documentation (don’t need to twice describe things).