You will need the Write Notes permission to perform this action.
Navigate to the person's profile whose note that needs to be edited and click on the Notes tab. Next, locate the note that needs to be edited in the table and click on the 3-dots menu at the beginning of the row and choose Edit. Alternatively, click on the date to open up the note.
A pop-up will appear where to edit the details of the note. See this article for more information on the fields.
Helpful Tip
Notes of type "Archived Notes" and "Unarchived Notes" cannot be edited.