To exchange an item, visit any store on Jorvik and drag the item you wish to exchange to the box with the hand icon that is located in the bottom right corner of the shop window. A pop-up will appear to ask you to confirm that you wish to excahnge the item and also show how much Jorvik Shillings you will receive from the exchange.
Please be aware that items that have been excahnged or thrown in the trashcan cannot be restored.