If you want to add an event via a Joomla menu item you will need set it up this way.
1. Make sure the javascript is loaded.
In your template's index.php file ensure you have the following lines - you could put them just after the
defined( '_JEXEC' ) or die( 'Restricted index access' );
JHTML::_( 'behavior.modal' );
JHTML::_( 'behavior.mootools' );
JHTML::script('editpopup.js','components/com_jevents/assets/js/');
2. Create a menu item of type "external link" with the following in the link field
javascript:jevEditPopup('index.php%3foption=com_jevents&task=icalevent.edit&tmpl=component',800,500);