You may return a product within 14 days of receiving it, without giving a reason. Tell the shop (from your order or by email/phone) and send the product back within 14 days of your notice, unused and, if possible, in its original packaging.
The cost of returning is borne by the consumer unless the shop states otherwise. The refund is made by the original payment method within 14 days of your notice (the shop may wait until it receives the product).
You are liable for any loss in value from handling beyond what is needed to establish the nature and functioning of the goods.