You can easily add a form to your pop-up box by using Gravity Forms. If you need help with Gravity forms, learn to set up a form and set up form confirmations first.
Add Form to Pop-up Box
Once you have your form created and all the proper notifications and confirmations in place, create or open up a previously created pop-up box.
Place your cursor where you’d like your form to appear. Select the “Add Form” button above the editor options.
Select the Form you’d like to add to your website and click blue “Insert Form” button.
If you’re form is a brand new form, finish going through the Pop-Up Settings. Once done, be sure to hit “Publish”.