Hi. Can you be a bit clearer. It doesn't show you've sold anything. Have you sold something on another account or are you the buyer? You'll need to give more information
Generally speaking, you can add postage to an invoice by using the dropdown near the listing. Select 'send invoice', then add your postage amount to the invoice, then either preview (then send) or send. Don't press recalculate.
Assuming you're the seller. Only the seller can invoice
