By default CMS pages are visible by everyone. But you can enforce two kinds of view restrictions
1. Require login - to do this set Secure property of the page to true
2. Require members of specific groups - to authorize only specific group members to view the cms page, use the VISIBLE_TO_GROUPS property. Enter the comma separated group ids of the groups that you like to authorize.
Both the above changes needs CMS Site publish to be performed before the change becomes effective.
