Using an authenticator app

To use two-factor authentication, you will need to install a TOTP app, such as:

From the preferences screen, in the Two Factor Authentication section, click the Manage button
Find the Set up Authenticator App section and click the Set Up button
Install an authenticator app (if you don't have one yet)
Such as Google Authenticator, 1Password, Authy, etc
Scan the barcode into your authenticator app
Enter the code from your app
This is to confirm that the TFA code was added correctly
Click the Verify and Enable Two-Factor Auth button

Login Screen

When logging in you will need to open your authenticator app, then enter the code from the app.