You add a note by clicking on a message in your stream. A screen will appear on the right where you can place the notes.
In the Notes section, you can add new notes and find any previously made notes at the Conversation or Contact level. You can also place this note next to the Reply as a Note.
When you add a note, it remains visible in the information to whom you added the note. Use notes when you want to share important information about a sender with your colleagues or other users in your environment. You can attach multiple notes to a sender.
It is possible to edit or delete notes; click on the pencil icon or the trash can to do so. To do this, you must check the 'Edit and/or delete notes' right for the respective role.
Watch this video to learn more: