Go to the Order Screen for the order you need to cancel.

If you have already created any Fulfillments for the order they will need to be deleted. To do that click the fulfillment number in the Fulfillment Box:

Then, on the Fulfillment Screen, click the Delete Fulfillment button:

Once all Fulfillments have been deleted, click the Actions button on the Fulfillment Box and then Cancel & Refund:

This will send a request to your Payment Processor to cancel the charge.

IMPORTANT: This does not cancel the order with your distributor if you have already submitted it to them. You will need to contact your rep and ask them to cancel it.