Lock your notes on Mac
If you use upgraded iCloud notes or notes stored on your Mac, you can lock notes you want to keep private, so only people who know the password can view them. You create a single password, and then use it to lock or unlock any note. If your Mac has Touch ID, you can also use it to unlock your notes.
WARNING: If you forget your password and can’t use Touch ID to unlock your notes, you can’t view your locked notes.
Set a password
To lock notes, you need to set up a single password, used for both your iCloud notes and the notes stored on your Mac.
In the Notes app
on your Mac, choose Notes > Preferences, then click Set Password.Enter a password in the Password field, then enter it again in the Verify field.
Enter a hint to help you remember the password.
The hint appears if you enter the wrong password three consecutive times.
Important: It’s highly recommended that you add a hint. If you forget your password, and you can’t use Touch ID to unlock your notes, you won’t be able to view your locked notes.
Click Set Password.
If your Mac has Touch ID, select Use Touch ID to be able to use your fingerprint to unlock your notes.
Lock a note
Once you set up a password, you can lock your notes.
In the Notes app
on your Mac, select the note you want to lock.Click the Lock button
, select Lock Note, then enter the password (or use Touch ID). If you have a trackpad or a Magic Mouse, you can also swipe left with two fingers on the note (in the list of notes), then click the Lock button .If you’ve already entered the password during this session of Notes, you don’t need to enter the password.
To remove the lock from a note, select the locked note, click the Lock button , select Remove Lock, then enter the password (or use Touch ID). If you have a trackpad or a Magic Mouse, you can also swipe left with two fingers on the note (in the list of notes), then click the Remove Lock button 
.
If you can’t lock a note
You can’t lock any of the following:
A note you’ve added people to.
A note that has a video, audio file, PDF, or document attached. Only tables, images, sketches, inline drawings, scanned documents, maps, or web attachments can be included in a locked note.
A note stored in an iCloud account that hasn’t been upgraded. See About using iCloud Notes on Mac.
A note stored in an iCloud account that uses a Managed Apple ID. For more information about Managed Apple IDs, see the help for Apple School Manager.
View locked notes
In the Notes app
on your Mac, select the locked note, then enter the password (or use Touch ID).After you enter your password, all locked notes are unlocked, so you can easily view them without entering the password as long as you’re working in Notes.
To relock all locked notes again, choose Notes > Close All Locked Notes. If you don’t relock notes, they’re locked automatically after a period of inactivity or when you close Notes.
Change your password
In the Notes app
on your Mac, choose Notes > Preferences, then click Change Password.Enter your current password in the Old Password field.
Enter your new password in the New Password field, then enter it again in the Verify field.
Enter a hint to help you remember the password.
The hint appears if you enter the wrong password three consecutive times.
Important: It’s highly recommended that you add a hint. If you forget your password, and you can’t use Touch ID to unlock your notes, you won’t be able to view your locked notes.
Click Change Password.
All locked notes are updated to use the new password.
Reset your password
You should only reset your password if you’ve forgotten your current password, but still want to lock your future notes. Notes that are already locked still have the password in effect when you locked them.
Tip: It’s highly recommended that you change the password (see “Change your password,” above) rather than reset it. When you reset the password, you have to manage multiple passwords, and you can’t easily tell which note is locked with which password.
In the Notes app
on your Mac, choose Notes > Preferences, click Reset Password, then click OK to confirm.If this is an iCloud account, enter your iCloud password, then press Return.
Click Reset Password to verify that you want to reset the password.
Enter a password in the Password field, then enter it again in the Verify field.
Enter a hint to help you remember the password.
The hint appears if you enter the wrong password three consecutive times.
Important: It’s highly recommended that you add a hint. If you forget your password, and you can’t use Touch ID to unlock your notes, you won’t be able to view your locked notes.
Click Set Password.
If you reset the password, when you view locked notes, entering the latest Notes password only unlocks notes that use the same password. If some of your notes use an earlier password, you must enter that password to view them.