These are the settings in File>Setup>System>System Defaults



In User Security, click on the option Use Multi-Factor Authentication and input the user’s mobile number and then Save the changes.



When the user attempts to log in, they’ll receive this prompt and type in the key that was sent to their phone


If successful, they will be logged in.


If they input the wrong key they’ll see this:


Too many failed attempts will cause this:


To unlock the user, go to User Security and click Unlock MFA