This feature is only available in the Enterprise version of the product.
Security policy is a tab on the Administration settings screen.
The setting is summarized in the table:
|Disable login for user account if not used for X days||Inactivity period (days)||A checkbox used to disable login for a user if he has not been using his account for X days in a row, with a sub-setting which sets the length (in days) of the inactivity period.|
To cause the above setting to take effect, use the 'Apply' button.