This is a client-side map style for use with OpenStreetMap data. The style can be broken down into two parts: the client-side rendering rules, and the server-side vector tile definitions. As such, it's like two projects in one, which are closely coupled.
Load the data and install the software as instructed in the vector README. Run Tegola.
Check that http://localhost:8080/
has a Tegola preview page.
Serve the client style with cd client && ./serve.py
and open http://localhost:8081/
in a web browser. Detailed instructions can be found in the client README.