Menu: System and API Setting, then Security.

Page title: Enable 2 factor authentication.

This adds a second check at login. After the password, the person must enter a code sent by email before the account opens.

Enable 2 factor authentication: Yes turns the email code on for login. No leaves login as username and password only.

2 factor authentication time: How many seconds the code stays valid. The minimum is 100 seconds. Example: 300 gives five minutes to enter the code.

Click Save.

Before you choose Yes, open Email API Settings and confirm the API key is saved. This page shows API Key Not Found and a link to Email API Settings when the key is missing. Without it, the login code cannot be emailed.