Multi-factor authentication can be enabled in Salesforce by navigating to Session Settings in Setup and adding Multi-factor Authentication to the right column before saving. A permission set must then be created and assigned to users, which allows enabling the "Multi-Factor Authentication for User Interface Logins" system permission.

1. MULTI-FACTOR
AUTHENTICATION
IN SALESFORCE
How to enable 2-factor authentication in Salesforce
Navigate to Setup > Session Settings >
add the Multi-factor Authentication to
the right column > click Save
Go to Setup > Permission Sets >
click New > enter the Permission
Set name > click Save.
Find System Permissions in the System
section > click Edit > enable the “Multi-
Factor Authentication for User Interface
Logins” checkbox > click Save.
Assign the Permission set to
the appropriate users.