This application isn't meant to be run by itself. The correct process is to clone the backend repository here. When cloning the backend, be sure to clone it recursively as this frontend repository is a submodule of the backend repository.
Read the backend repository README such that you know how to configure the settings of the application, and then simply run it through an IDE (or dotnet run via CLI). This will start both the backend .NET web server, as well as build and serve the frontend.