What is best way to create Business expense invoices?

I have a Limited Company, and have been recording my business mileage on a spreadsheet. I then create an invoice within Quickfile, and then I Invoice my Customer/supplier who is paying for the travelling I am undertaking.

I now want to use Quickfile for travel. I have followed the guide below for entering my first travelling expense.
http://help.quickfile.co.uk/main/1/business_mileage.htm

How do I now log this payment to my Customer/supplier Invoice details in Quickfile?