https://github.com/paulb777/nextjs-firebase-codelab.git
The codelab has the full instructions, but as a quick start, you can do this.
firebase emulators:start --project demo-codelab-nextjs
lib/firebase/config-copy.js to lib/firebase/config.js and fill in the values from the Firebase console.npm i
npm run dev
http://localhost:3000http://localhost:3000/ within your browser, click the "Sign in" button in the top right corner and sign in.