Denice: Any tips?
At this point you can view your invoice from the Invoices tab link either from the Field Service Center or Customers tab. While viewing the invoice you can Save & Email button to send this invoice to the client. The email will contain a link to login to your portal which will allow them to view/pay that invoice provided you've setup a payment gateway.
I'd suggest setting up a payment gateway next if you're looking to accept payments online.
~C