To provide additional protection of your account from unauthorized access (for example by former system administrator, disgruntled husband or wife, competitor), the two-factor authentication is used.
How to enable two-factor authentication?
You don’t need to enable this service, because it’s set for all users by default.
How to add new phone number?
To change the phone numbers that are used in two-factor authentication, you can in the MIrohost control panel.