Fatal error when dashboard menu link "Pop Overs" is clicked

Just uploaded and activated the pop up plugin. When I navigate to the dashboard > Pop Overs, I saw the following error:

Fatal error: Call to undefined method stdClass::add_help_tab() in /home/my-account-name/public_html/my-domain.com/wp-content/plugins/popover/popoverincludes/classes/popover.help.php on line 53

URL:
http://www.my-domain.com/wp-admin/admin.php?page=popover