Apart from the bank connection, which automatically imports the latest transactions every day, you can also manually upload:
bank statements, which can be downloaded from your internet banking platform. Do this if you cannot find your bank in the list provided by ThinkOut or if you are not ready to connect it yet;
sales reports;
invoices that are not collected/paid (will become forecasts for your cash flow);
a database with your cash transactions;
your forecasts for the next period;
any other reports and documents that help you to get a complete picture of your financials.
Keep in mind that any file you want to import in ThinkOut must be a CSV/XSLX/XLS.