Thanks @pumrum for the excellent reply.
The only detail I’ll add is that you can (optionally) include a “Category” column if you like, as long as your entries in this column exactly match the top level category or sub-category on Stessa. Since all sub-category names are unique, you can ignore the top-level category if using subs. The “Description” column is different and like @pumrum says, will populate the “Notes” field in the Transactions ledger.
You’ll find a full list of all categories available on Stessa here: Stessa Categories: Master List
Finally, the CSV uploader does not currently support a “Property” column, so you’ll want to separate each property’s data into a separate CSV document and then upload each in turn with the correct property address selected in the upload window.
Further details on CSV uploads are available here: Upload Transactions Data (QIF, CSV)