In order to enable generation of invoices (factura electrónica) via LibreDTE, navigate to Property Settings / Integrations and select LibreDTE section.
The details which you need to enter there must be obtained from Libre DTE account (https://libredte.cl/usuarios/perfil).
When the connection with LibreDTE is active, you can generate an invoice (Boleta or Factura de exportación) while taking payment.
Once the payment is taken you will be able to see the invoice number and open in from three places:
1) Payments tab in the reservation window:
2) Accounts and Transactions:
3) All Issued Invoices when you double click on the invoice: