Notes are added to authority records through the Cataloguing module and use the 667 - 688 fields. You’ll find a list of these fields here.

The most commonly-used fields are:

• 667 - Non-public general note (displayed as Cataloguer Notes).
• 680 - Public note (displayed as Scope Notes).

Here's an example of the Full Display of an authority with cataloguer notes and scope notes.

Here's the same authority in the Cataloguing module.