Ctools Automodal will help you to create popup in your site. It is an easiest way to create a popup without any burden. To Create a popup form please follow the below instruction:-
Download and install the ctools Automodal(module) in your drupal instance.
Description : By using this module You can create your own custom form in popup.
The below example shows how to redirect a user after login. This example code will not be affecting the password reset functionality of Drupal core.