From the documentation, you have to use the shortcode:
[fc id='12' type="popup"][/fc]
Next, something has to trigger the form, you can create a button for that and then click it from jQury, edit the link which would trigger this form, and put the href or hyperlink to:
<a class="triggerForm" href="http://yoursite.com/form-view/12">Link Trigger</a>
jQuery trigger.
$(document).ready(function () {
$('a.triggerForm').click();
});