Hello,
If you want to set up and accept crypto payments, you can enable the Coinpayments option from the Admin CP -> Payment Options page. You don't have to edit the file manually. If you want to know the file to handle the payment, it's available in the sandbox.php file, under common/ folder.
Regarding the auto-withdrawal feature, this feature is not currently available in the script. In order to implement it, it would require customization service. This is because some payment options do not support it, and the rest of the payment processors have a different method for auto-payments.
Regards,