Attempting to add Mailchimp signup in lightbox on Jumbotron button

I am attempting to find the location of the Jumbotron buttons for inputting a lightbox popup that would be linked to a MailChimp signup form.

Utilizing THESE instructions, I am attempting to have one of my buttons be linked to a popup box using Easy FancyBox plugin.

I cannot find the location of the php that I need to insert the code to. Please help! Support for this theme has been amazing so far! thank you for all your help.

Website is here.


The location of the jumbotron buttons is inside the theme folder > sections > front-page-bottom-header.php

Let me know if you got it alright.