Actually, there are two separate apps. The Client which serves the FrontEnd (using React), and the Server (in Node/Express).
# Navigate to the server directory
cd server
# Install dependencies for server
npm install
# Install dependencies for client
npm run client-install
# Run the client & server with concurrently
npm run dev
# Run the Express server only
npm run server
# Run the React client only
npm run client
# Server runs on http://localhost:4000 and client on http://localhost:3000