How do I add someone as an authorized user to my Credit Card? 

To add an authorized user to a credit card account, submit a signed written request. The request must be signed by both parties: the original card holder and the person to be added as an authorized user. The form can be returned via Online Banking Secured Message, faxed to 206.398.5679, dropped off at a branch, or mailed to Seattle Credit Union, PO Box 780, Seattle, WA 98111-0780.