It's a text file, you can download it and edit it using a basic notepad or text edit type program.
You do NOT want to use a word processor for this.
Carefully make the changes as suggested by wocommerce and upload the file back to the root of your WP install.
Some FTP clients will let you view and make simple text edits to files right there at the server (Dreamhost,your website). If your's does, view (edit, open) the file, make the changes and save.