The Below Code will show you how you can create the Popup Window in Liferay.we have given the id **patient-popup** to the popup window and enable that window on onclick event of link button.

View.jsp

<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %>
<%@ taglib uri="http://liferay.com/tld/aui" prefix="aui" %>
<portlet:defineObjects />
<script src="http://code.jquery.com/jquery-1.11.3.min.js"></script>
<style>

    /*  popup */
    .patient-popup > h2{ color:#fff;}
.patient-popup {
  display: none;
  background: #333;
  border-radius: 7px;
  bottom: 0;
  height: 160px;
  left: 0;
  margin: auto;
  position: fixed;
  right: 0;
  top: 0;
  width: 370px;
  z-index: 11;
  padding: 0 14px; }

.patient-popup h2 {
  font-size: 20px;
  text-align: center; }

.portlet .patient-popup .button-holder {
  margin: 0 auto; }

.portlet .patient-popup .button-holder .btn {
  float: left;
  padding: 5px 3px;
  font-size: 16px;
  color: #fff; }

.portlet .patient-popup .button-holder .btn.btn-cancel {
  color: #000;
  margin-right: 3px; }

.overlay1 {
  width: 100%;
  background: #000;
  opacity: 0.4;
  height: 100%;
  position: fixed;
  top: 0;
  left: 0;
  display: none;
  z-index: 10; }

.aui .patient-popup .button-holder {
  width: 129px; }

.aui .patient-popup .btn.deleteRecord {
  float: left; }

.aui .patient-popup .btn {
  color: #000000 !important;
  font-size: 14px !important;
  padding: 1px 9px !important; }



</style>

<script type="text/javascript">

function showPopup(){
    //alert('open popup');
     // $("body").trigger("click");
      $(".patient-popup").show();
      $(".overlay1").show();


}
function closePopup(){
      //alert('close popup');
        $(".patient-popup").hide();
        $('#message h2').html("");
      $(".overlay1").hide();
      //$(".docDetails").hide();
}


</script>

<aui:script >

 Liferay.provide(window,'clickOK',function() {  


     $('#message h2').html("Complete the Demo of Popup Window");
     $(".patient-popup").hide();
     $(".overlay1").hide();
 },
  ['aui-io']
); //End of Provide 
</aui:script> 


<a onclick='showPopup();' href='javascript:void(0)'>Click to Open PopUp</a>


<div class="patient-popup">
            <h2>This is Popup Message</h2>

            <aui:button-row>
                <aui:button type="cancel" value="Cancel" onClick="closePopup();" />
                <aui:button cssClass="deleteRecord" type="button" value="OK" id='' onclick='clickOK();' />
            </aui:button-row>
</div>

<div id="message">

        <h2></h2>

</div>

<div class="overlay1"></div>

Below screen-shot show the pop-up window using liferay.