I received an order weighing more than 1 panda, how can I add the amount for
shipping to the invoice?
As long as it was an instant checkout, you can still make updates. Go to your
orders page and add the amount to the "shipping" block then apply it
to the order. When you generate your invoice now that amount will be part of
the total.
As long as it was an instant checkout, you can still make updates.
Presumably meant to be WASN'T.
To the OP, if it wasn't instant checkout and you are putting the shipping
price in on the order summary page, make sure you click the button to update
it before sending the invoice.