1. On the united.com home page, enter the origin, destination and travel dates. Select the "Search" button.
2. Choose your flights and enter your contact information.
3. When you reach the Payment information page, select "United payment types." You will see the option to redeem a travel certificate. Select year of issue, enter PIN and recipient’s last name. To redeem the certificate, you must click "Apply." Certificate amount will be deducted, and then payment for any additional amount owed can be entered to complete your ticket purchase.