how to make a free shipping discount apply to specific products?

I see there is a free shipping discount option (if you set it to 100%), but there's no place to apply this to products that I can find (only roles).  Is there a way to do this with NC 4.2 ?

You can create a new discount with discount type “assigned to shipping” at promotion - discount and set 100% in the discount percentage. After that in the discount requirements type select “must be assigned to customer role” and select the roles you want to apply free shipping. After saving the discount, map the discount and product.

Okay, I get the first part. There is no place to map the products to the discount.  I can't find it on the product pages --> It says [No discounts available. Create at least one discount before mapping.] or in the discount section. Is there another setting somewhere to do this?

This is all or nothing. You cannot specify shipping discount to specific products/categories via a discount, unfortunately, only via a customer role (which is for ALL products).  You can, however, go to each product and tick the free shipping box, (what we do) and go from there, unfortunately, if you have a lot of products, this could take a very long time.