On the Orders section of your AppScenic Account, you have all your orders.

If the order hasn't yet been shipped by the Supplier (it should have the status 'On Hold' or 'To Be Shipped') you have the option to cancel it. 

Find the order you want to cancel and on the other side of it click on the CANCEL button, placed under the ACTIONS column.

Choose CANCEL, then confirm your choice and that's how to cancel an order.

Simple, right?