A quote from the co.com website (Home > Products & Services > Continental Airlines Credit Card from Chase > Current Continental Cardmembers)
Simply follow these three easy steps to receive your 5% discount:
1. Visit continental.com
2. Sign in using the OnePass account number and OnePass PIN associated with the primary credit card account
3. Enter Offer Code "OnePass" in the Offer Box on the continental.com homepage.
4. Search for your desired flights.
5. Pay with your Continental Airlines MasterCard at the point of sale.
Offer valid for Continental Airlines MasterCard Credit and Debit Cardmembers.
Sounds like a good deal, but reading this, it's unclear if I trust their quantitative skills. Maybe it's 5 easy steps and 3% discount :-)