You should have already followed the Display new user data in user list page recipe to have a starting point for this recipe and the resulting plugin should still be active in your development site. Alternatively, you can get the resulting code (Chapter 7/ch2-private-item-text/ch2-private-item-text-v5.php) from the Chapter 7, Customizing User Data section of the downloaded code bundle, renaming it as ch2-private-item-text.php.