You can access the Encryption for Email Preferences screen:
From the Encryption for Email Tray Tool menu, as described in Using the Encryption for Email Tray Tool Menu
From the Preferences icon in any Encryption for Email application, such as your email program, as described in Using Encryption for Email in Your Email Program
Note: When using Encryption for Email in a corporate environment, your corporate administrator might have set the values of some sections for you and hidden some controls from view.