Adding a Pop-up Trigger
To show a popup on button or link click on do that from the Link Picker. You have the option to select Popup and select the popup name that you gave when creating the popup.
(https://s3-eu-west-1.amazonaws.com/cdn.supporthero.io/article/2618/2c8eb23e-c1fa-4e5f-9e24-aa9cb17f57c7.png)