There are a few different ways that you can password protect a CSV file.
One way is to use a third-party program like 7-Zip or WinRAR to compress the file and then add a password to the compressed file.
Another way is to convert the CSV file into an encrypted PDF using a program like PDFMate. Once the file is converted, you can set a password for opening the PDF.
Or, you can use Microsoft Excel to save the CSV file as an .xlsx workbook, which can then be password protected.
Whichever method you choose, make sure to remember your password so that you can access the file later!