Firstly, you need to pair the Google 2fa mobile app with your profile.
The Google Authenticator device does not sync your 2FA information to Google servers and runs independently on your device.
Pairing simply involves scanning a barcode which is displayed in profile settings by the Google 2fa mobile app.
Within a few milliseconds after scanning, the Google 2fa code is generated on your mobile.
Remember, while scanning the barcode, a secret key is also mentioned on the same screen. Do note that secret key or simply take a screenshot o that screen. It is used in case you have lost or damaged your mobile phone.
Pairing is not difficult and anyone can pair up within 2 minutes. Simply follow the instructions outlined.
After pairing, when you try to log-in next time, you will need to enter the code running on the Google 2fa mobile app after entering your username and password. The code changes every thirty seconds thus improving security measures.