Navigate to your Firebase console, and copy your project Firebase Config. Then pass it to the initializeApp method. For example, this implementation shows Google Auth:

const app = initializeApp(firebaseConfig);

        const auth = getAuth(app);
        useDeviceLanguage(auth);

        const provider = new GoogleAuthProvider();

        const R = await signInWithPopup(auth, provider);

To find your Firebase Config, go to this link, then select your project. Now go to the bottom (your apps section), select the config option from the SDK setup and configuration menu, and copy it.