Go to some google service > profile menu dropdown in the top right > manage your google account > security > signing in to google > security > 2 step verificati

Go to some google service > profile menu dropdown in the top right > manage your google account > security > signing in to google > security > 2 step verification. You can then 'add more second steps to verify it's you' including an option for an authenticator app (i.e. totp). Also worth generating some backup codes while you're at it.