Creating an invoice is easy. Once logged in to the admin panel, go to Invoices -> Create Invoice.
Enter an invoice number (auto-increments from last invoice), choose a client from your existing clients, and choose from some options.
When your invoice is all filled out, click Create Invoice. Don't worry if you make a mistake, it hasn't been sent yet - you can still view and edit it all you want before your client gets it.
When its ready to be sent, click the envelope icon from your invoice list.
Let Pancake send your new invoice to the client using the default settings, or quickly change the wording to suit your style. Hit send and you're one step closer to being paid.