Returns can also be handled like any other order on Amazon, you could print a return label for the customer via the amazon order or you can have the customer return the order to you. Its your choice. But the Amazon return label will go to an Amazon warehouse, while you could have the customer return it to whomever you like if you handle things.
If you ship returns to a Amazon warehouse you will use Amazon Seller Central to create the return label and process the return. FBA Shipping does not manage returns for you.