Henry T. Casey:

Not all of your files are meant to be seen by everyone. Your friends and family may not appreciate this truth, but that’s just the way it is sometimes. Luckily, MacBook owners can protect their sensitive files from prying eyes by password protecting specific folders.

Every Mac owner should know how to do this. I only wish Apple would offer a more direct method of password protecting a folder, one that didn’t require the creation of a separately mountable volume. But this solution works and works well.

That said, if you are trying to protect text, as opposed to a set of files, consider placing that text into a note, then locking the individual note. This has the advantage of giving you access to that protected information on your Mac and all your iOS devices.

Here’s Apple’s support doc on adding a password to your notes.