ISUPPLIER PORTAL-SUBMIT INVOICE FOR NON PO

I want to know if someone worked with the the "SUBMIT INVOICE FOR NON PO " process. I did not find any documentation about the process.

Oracle iSupplier Portal and Payables Request Invoice Approvals
Invoice approval workflow is required for self service invoices that are not matched to a purchase order. These invoices are created using Oracle iSupplier Portal or the Payables Request responsibility. The system initiates the approval process automatically when the invoices are submitted. At this point, the invoice becomes an invoice request. The approval workflow must be complete before the invoice becomes a standard invoice. Once the invoice becomes a standard invoice, the system validates it and the invoice is susceptible to holds. The requester name on the iSupplier Portal can be the first approver in the approval chain.