I'd like to make sure we're on the same page. When you say load receipts, are you trying to import your bank transactions? If so, you'll want to download your transactions as a CSV file, or check for an app on how to convert PDF to CSV.
When you connect your bank or credit card for the first time, QuickBooks Self-Employed downloads the last 30 to 90 days of transactions, and in some cases up to a year.
Once you have the CSV, go to Transactions > Import Transactions. Please see this sample screenshot for a visual reference: