Well thanks guys.
For anyone new reading this topic actually wanting to know the answer:
You don’t need the invoicing app advertised in the Fiverr app. You don’t need to do anything.
You deliver the goods and the customer pays Fiverr who then deposit a small percentage of the order charge to you, holding the rest back in case of any disputes, which then gets deposited in your account at a later date if there are no disputes.
Why none of the above respondents could actually say that instead of unhelpful saying “read the help files” or even provide the link to the page on the help files that explains this (since I had clearly said at the top of my post that I had read the help files and couldn’t find anything explicit that explained how the payment process worked) I don’t know. But since I have now experienced it, I have provided the answer for other first timers.
Good luck to all you other noobs out there.