How do I add postage to a listing that has sold and been paid for?

[justlookn4me]

Pick Up Only item.  Buyer asked if I would post which I said I would and gave a rough postage cost to do so.  Buyer has bought and paid immediately on the Pick Up Only price.  How can I invoice for the postage costs as I don't see an option to do so?

[kopenhagen5]

Log into PayPal and do a funds request if the buyers PP email is showing in the transaction.

If not, ask the buyer for their PP email so you can send a funds request for the postage amount.

The buyer should be able to message their email as you are in a transaction already.