All mainbuyers received an email with more information about how to request a refund. Please also check your spam-folder, the email could end up in there. You will be able to request a refund via the button in the email or via this link.
Please be aware of the fact that only the mainbooker can request a refund for the full order. Besides that, refunds can only be processed by order and not per ticket. This means you have to keep or refund your full order.