To use Google Authenticator, follow these steps:

1. Download and install the Google Authenticator app on your mobile device from the App Store (iOS) or Google Play Store (Android).
2. In the online account you want to secure, go to its security settings and enable Two-Factor Authentication (2FA) or Two-Step Verification.
3. The account will show a QR code or a secret key for setting up 2FA.
4. Open the Google Authenticator app, tap the "+" button, and choose either "Scan QR code" to scan the displayed code or "Enter a setup key" to input the code manually.
5. After scanning or entering the code, the app will generate a 6-digit code for that account.
6. Enter the 6-digit code into the online account setup page to confirm and complete the setup.
7. Going forward, when logging in, after entering your password, open the Google Authenticator app to get a new 6-digit code and enter it to verify your identity.

Additional tips:

• You can add multiple accounts to Google Authenticator.
• The app works without an internet connection once set up.
• You may optionally sign in to your Google Account within the app to back up and sync codes across devices, but this has some security considerations.

This process adds a second layer of security by requiring a time-based one- time code generated by the app along with your password, significantly improving account safety.