If you've encountered a CSV file and you're unsure what they're for, the good news is they're pretty straightforward and easy-to-use with apps you already know.

Apple Passwords import is simple. Export CSV from your old manager then use Passwords app File Import. Delete CSV after import for security.

From here, click File > Export to Google Spreadsheet. Google Docs will convert the CSV back into a spreadsheet and you'll be able to open it and work on it in no time.