Customize popup for one page

Hi, I want to customize design of popup only on login page, popup should be open at top not in center and 100% width, but i don’t understand where i apply classes for that. Plz help me to solve this issue.

Use the cssClass option when you create the popup and then add this style:

.popup-login .popup {
  width: 100% !important;
  position: absolute;
  top: 0;
  left: 0;