How do I request a final invoice?

[Mckayz]

I am buying a few things from the same eBay shop. It says that in order to combine postage I need to send them a final invoice.

But I'm not sure how to do that?

Thanks

when you go to pay in paypal you can click request total from seller - you can also do it from my ebay I think using drop down menu next to the item

Thanks