Clone the directory and cd into it.
Run npm install -g electron to get the required electron version on your system (the node_modules are already included, if for some reason you need to delete these, run npm install to download the node modules from the package-lock.json file).
Before you can run the app, you have to transpile the .jsx files in src/* into .js files in a directory which will be created called dist/. This is all taken care of with the npm start command.
To run the full app run npm start