To Remove a shared or local credential,

  1. From the menu bar, select Tools -> System Administration.
  2. Next, select Global -> Credentials. The Global Shared Credentials window displays, with a listing of pre-assigned, shared credentials.

    globalremovex

    At the bottom of the window are the View Associations, Roll, Add, Edit, and Remove buttons, along with the Close option.  

  3. Select a credential from the list, then click Remove
  4. At the Confirmation message, click OK.

See Global Shared Credentials for more information.