If you have your data in Excel, you’ll want to use the import option for CSV files. Just make sure your columns match up with the following criteria, and you can import them through Account Settings > Import Data > Import Purchase Invoices
Criteria for the CSV can be here:
http://community.quickfile.co.uk/t/importing-sales-and-purchase-invoices/8885
[Edit]
Just a note - it may seem obvious, but don’t forget to save file as a .CSV rather than .xls or .xlsx