You cannot send eInvoices to you customers unless they are also registered for eInvoicing and you know their ABN/NZBN/UEN/VAT number. Similarly you can only receive invoices from suppliers who are registered and know your number.
These numbers numbers need to be stored in MoneyWorks against each participating customer/supplier.
Find the customer/supplier in the Names list and double-click to open
Enter the number in the eInvoicing ID field on the Bank and EDI tab