First, cd client and run yarn install. Then run yarn start to start the frontend.
Then, in a separate terminal window, cd ../server and run npm install.
Then run npm start to start the backend.
Finally, go to localhost:3000 to see the website.
Install packages in the frontend using yarn add <package> in the client/ directory.
Install packages in the backend using npm install <package> in the server/ directory.
If you're working with mongo, run mongod in a separate terminal window before
starting the backend. Data will be saved into a database called shake-shack.