Beginning selling as a business.

I run my family business and we haven’t ever sold on Amazon.

I’d like to sell commiunion wafers, disposable communion cups and possibly a few other items (mostly) churches would use.

How does shipping work, do I set my own prices? Since these categories don’t seem to be listed individually, would they likely pay the 15% fee upon sale? How do payments work?

I might also sell books, not only those for my usual business customer.

Thanks for your help in advance.