Go to the candidate's profile on which you want to add a note.
Start writing a note - and in the place where you want to tag another user, use the β@β sign. A list of users and Hiring Managers will expand, from which you can choose who you want to tag:
After selecting the right user and entering a note, click βAdd Noteβ and it will appear on the timeline below.
The tagged person will receive a notification in the upper right corner of the system informing that he has been tagged in a note. He will also receive an email notification if he has selected he wants to receive it in user settings: