Gated popup on button click

Hello

I'm looking to add a popup to a button that, when pressed, the pop up appears (with some descriptor text and maybe an image. The usual/normal Squarespace popups would do) with an email field where the user enters their email, then presses submit, and a whitepaper downloads. I've read a few posts on Cirlce, but it starts with a newsletter block. This is not what I want. 

This is the site and the blue Download Whitepaper button (currently, the whitepaper is not attached to the button): https://www.getwicklow.com/whitepapers

This is a simple marketing tactic; any help would be appreciated.

Use a Form block, set it to lightbox, and add the download link in the post-submit message or on a different page and use the post-submit redirect to get to that page. Or set the post-submit redirect URL as the PDF URL.