See the "Managing Shipping" chapter of this guide in order to learn you about shipping and carriers.
Note: Merchandise return is not enabled by default. If you want to allow your customers to return products and get a refund or a voucher, you can do it in the "Merchandise return (RMA) options" of the "Merchandise return" page, under the "Orders" tab.
Merchandise return is explained in the "Managing Orders" chapter of this guide.
Choose your theme
Your shop should have its own theme in order to have a distinctive style, and therefore be more recognizable, separating it from the numerous other shops online.