Embed donation form into donate page

Site URL: https://www.culikid.org/donate

The client wants to be able to add a descriptive paragraph to accompany the donation form.
See current page here: Donation Form

That is actually a /...secure.squarespace.com/checkout/donate... page.
I was able to customize the messaging [e.g. email field message, contribution field message, etc.] on that page but it does not allow for customizing, or adding additional text.

I created this page: https://www.culikid.org/donate

The outlined box to the right is where I have attempted to embed (it didn't take) with:

• <iframe src = https://secure.squarespace.com/checkout/donate?donatePageId=5934052903596eae57d12bda&ss_cid=10b04f94-b672-424a-ae11-be8030349c5c&ss_cvisit=1584056367364&ss_cvr=e273f501-7f00-4aa2-a980-d9611c646a43|1584030690847|1584035188051|1584056367497|3 width = "555" height = "200">
          Donation Form
        </iframe>

  I tried CODE as well. Wouldn't work.  Error message noted, "That page is no embeddable."

How can I have both text and the donation form on the same page?

You want to add a description under Donate form? 

or?