Paying invoice using imported transaction

[Nigel Sim]

How do I link a transaction, imported via QIF from my bank, to an
invoice in Accounts Receivable and thus mark the invoice as paid?

I tried the "Process Payment" menu item, but that creates a new
transaction in the source account, meaning I then have to delete the
imported transaction.

>From what I can tell I need to add the transaction into the
appropriate "lot", but all I can find is how to view the lots, not how
to manipulate them.

Regards
Nigel