Okay, I will try to explain what they meant in simple terms.
You CAN have and use a prop like this in your story, but it can not mention the brand name or would need to be altered (in this case, Chick-fil-A). The reason for this is because it would be copyright infringement - or the use of another brand’s product(s) without their permission since it is copyrighted.
Chick-fil-a owns that product (waffle fries) so you can’t use it for your own financial gain nor usage unless Chick-fil-A permits you, or allows you to use that image.
You are allowed to use these images however! Please, just take out the brand name (Chick-fil-a)