Trying to add pickup availability to Supply theme

[WebWorld616]

Using this guide https://shopify.dev/themes/delivery-fulfillment/pickup-availability

I am trying to add the pickup availability functionality to my product page, but am gaving a hard time figuring out how to call this fetch and from where.

The section that describes the javascript code shows the fetch call, and says

"In order to access the variant ID, and update the display when a variant is selected, you need to make a call to your pickup availability JavaScript function from the JavaScript responsible for updating product page elements on variant selection."

My question is, where is this location in the Supply theme? 
Thanks in advance,

(side quest)
I also attempted the mentioned implementation at the top of that link, that used the Dawn theme, but when I hacked it enough to get the availability showing, the variant selector disappeared... which I couldn't get the variant selector and availability messages showing at the same time.