If the order has not been processed -> Go to the Orders tab and select to Cancel the order from the dropdown list of actions. If the order contains multiple items, each item needs cancelled individually.
If the order has already been processed -> Contact firstname.lastname@example.org to request order cancellation. Please note if your order has already started processing we are unable to cancel the order.
Note: Cancelling the order in Customized doesn't cancel the Shopify order or process any of your customers refund. Those actions should take place inside of the Shopify order administration.