On the My Account > My Orders page, select the order for the product you want to return.

On the order detail page that opens, click the "Return" button in the field containing your order information.

On the return page that opens, mark the products you want to return, select your reason for return and click the "Return" button.

(For payment at the door, the form you will see on the same page must be filled.)

You can deliver your products free of charge by going to the cargo company you will see on the same page with the "Return Cargo Code" on the page showing that your return request has been received.