One message on each row
Each row of your file is one customer message. A ticket, a review, a cancellation note and a survey answer are each one row.
If your export has the customer's words in several columns, keep the one that holds the message and leave the rest. ClientClue asks you to confirm which column that is.
You do not need a spreadsheet at all. Paste messages one on each line, or save a plain text file with one message on each line.