Choose an authenticator.
There are many options when it comes to two-factor authentication. The most popular options include apps that can be downloaded to your iPhone from the App Store, like LastPassAuthenticator, Google Authenticator, or Authy. LastPass supports many two-step verification apps.
Enable 2FA on your iPhone
On your iPhone, go to Settings, then "Your Name", and "Password Security." Then turn on two-factor authentication.
Log in with extra protection.
After you hit "Continue," the next time you log in to the account, you will be asked to confirm your password and two-factor authentication, too. Enter the code from the app on your phone or tap the approval message sent to your smartphone.