Once two-factor authentication is globally enabled, navigate to the Weekly Rules page by clicking the Access Control button on the left navigation bar. From here you can either edit an existing rule or add a new rule to use two-factor authentication.
To enable two-factor authentication on a rule, simply enable the slider on any “Grant Access” rule type:
In the event that there are rules with overlapping schedules, the two-factor rule will always take precedence over the standard rule.