Hi ruthball-bookkee
You can either enter the transactions manually, or if you have the transactions on an Excel/CSV document you can import them into QuickBooks or connect your clients bank account and add the transaction into QuickBooks however the standard connection only brings 90 days of historic transactions, you can/your client can however download historic bank statements from their online bank, in an Excel/CSV format, delete any transactions you have already added into QuickBooks and upload them in to QuickBooks.