credentialSecret does not have any relation to how you secure the editor.
What have you tried so far? When you say it doesn't work what exactly do you mean? Does the editor prompt for a login but you can't get in? Or does it not prompt for a login at all? Have you restarted Node-RED to pickup those changes? Are you sure you're editing the right settings file?
If you are trying to setup a user called admin with a password hallo then it will not work because you need to generate a password hash. This is explained in the link shown in the comment in that screenshot.
But then I got the great idea of changing the password, so I generated another hash for new password.
I pasted that new hash into the settings.js and restarted node-red.
But now it looks like there is no password check anymore. I tried rebooting and wiping password from browser, but no password check anymore.