A user can activate a Discover credit card online, according to Discover. A cardholder can activate a credit card through her online profile or without logging into the system first. Alternatively, she can activate her Discover credit card over the phone by calling 1-800-DISCOVER.
To activate a Discover credit card through an already-established online account with Discover, the user logs in to the system and enters her user ID, password and three-digit sequence ID from the back of the card, according to the company's website. To activate a Discover credit card without first logging in, the user enters her birth date, the last four digits of her Social Security number, the entire 16-digit Discover credit card number, the expiration date, and the three-digit ID number found on the back of the card.