Adding code to a button

Hi,

I'm trying to add some code that was given by a provider to embed a pop-up form.

Button code:

zeffy-form-link="https://www.zeffy.com/en-US/embed/donation-form/f73f6a0c-1dd9-4583-91b8-0e08fa8e8488?modal=true"

And the following is inserted into the header:

<script src=https://zeffy-scripts.s3.ca-central-1.amazonaws.com/embed-form-script.min.js></script>

I'm trying to add the button code to the "Donate" button on the URL: https://hudcostreets.org/donate

Do I need to create a button from scratch using code blocks?