Shipping codes

I am having exactly this problem which is outlined on the help page.

Error sending invoices: “TaxType code ‘xxx’ cannot be used with account code ‘yyy’
You may see the following error in the order notes:

ERROR creating Xero invoice: ErrorNumber: 10 ErrorType: ValidationException Message: A validation exception occurred Detail: The TaxType code ‘xxx’ cannot be used with account code ‘yyy’.

If so, this is related to the shipping account being set to the wrong type in the WooCommerce Xero settings: it must match the account setting in Xero. You can set it in the WooCommerce > Xero settings option Treat Shipping As:

The problem is that I don’t have ‘xero settings’ as an option in my woocommerce settings. What have I done wrong?