<a href="#test-popup" class="open-popup-link">Show inline popup</a>

 <div id="test-popup" class="white-popup mfp-hide">
   Popup content
</div>

$('.open-popup-link').mouseover(function(){
  $.magnificPopup.open({
    items: {
    src: '.white-popup' // can be a HTML string, jQuery object, or CSS
 selector
  }
  })
});