When ever you sign in to your account or perform sensitive actions, you may be asked to
prove your identity. So, you can
verify Google account using an Android phone and make sure it's connected to the internet. Then, on the "Verify it's you" screen, complete the task or
choose "More ways to verify." Now, you will see some options like
getting a prompt sent to your phone and getting a verification code by text or
getting a security code on your Android device. Now, use your screen lock or
fingerprint on your Android device and enter a security key added to your
Google Account. Then, follow the on-screen instructions and use your phone when
prompted.
See also - Google authenticator new phone lost old phone
