Where: This change applies to Salesforce Classic, Lightning Experience, and all versions of the Salesforce app in Enterprise, Performance, Unlimited, and Developer editions.
How: Enable encryption when you create or edit a rich text area field.
In Lightning Experience, from the Object Manager, select your custom or standard object, and then select Fields & Relationships. When you create or edit a rich text area field, select Encrypted on the field detail page.
In Salesforce Classic, navigate to your object in Setup, and select Fields. Under the Custom Fields and Relationships section, click New or Edit, and select Encrypted on the field detail page.