How should I return the item should I choose to do so?

You’ll also need to securely repackage the piece in the original packaging (or if that is unavailable similarly secure packaging) and affix the prepaid label to the package.

You then have the choice of arranging for a USPS collection from your home address, posting it into any USPS postbox or taking it to a USPS Post Office where it will be immediately registered into their system and a receipt given confirming details. (recommended)