Using webhook to listen for an API callback that returns a file via multipart/form-data

I'm not sure if I am approaching this correctly.

I have an API that sends an API callback as a response.
To simulate this, I am using postman and defining a file in the form-data

In Retool, I have a trigger setup with a webhook endpoint and when I get this payload, I want to take the file and put it into Retool Storage for now. I figure if I can get that working, moving it elsewhere should be a similar process.

But I am not sure how to handle the payload when the API is called. The data looks like this: