The easiest way is via nvm, but it's up to you: https://docs.npmjs.com/downloading-and-installing-node-js-and-npm.
After cloning the repo and installing NodeJS, you can install everything necessary to build and develop by running:
npm install
Once that is complete, create a file named .env in the project's top-level
directory, which holds environment variables used by the app.
// Firebase server to connect to when running and developing. You can get this
// JSON from https://console.firebase.google.com/project/<project-name>/overview
REACT_APP_FIREBASE_CONFIG='{"apiKey":"","databaseURL":"","projectId":"", ... }'
// If you create assets for cards, etc. you can reference them here.
REACT_APP_ASSET_URL_PREFIX='http://www.foo.foo/'
Note: .env file values are not escaped for you, so wrap any values with
whitespace in quotes and escape any special characters (for bash).
From the project's top-level directory, you can run the following commands:
npm start // Starts a dev server at http://localhost:3000. Ctrl+C to stop.
npm test // Runs tests, of course.
npm run build
rsync -av --chmod=D2775,F664 build/ <user>@<domain>:<absolute-path>/
Note: npm run build uses your .env file(s) to build, so make sure you
understand how
dotenv environment variables
work before building (or you might, say, point production at your development
Firebase instance).
This project was bootstrapped with Create React App. Many of your questions can be answered by looking at the Create React App docs or readme.