Select "Card" from the top menu on the home screen. Below the virtual card, you'll see a button to "Freeze Card." This will protect your card from being used if found.
Select the "Manage my Card" card button and launch the Help Center. On the bottom of the page, submit a ticket and select "yes" to the question, "Are you reaching out to report a lost or stolen card".
Once a new card is processed, a virtual card will be available for use right away and a physical card will be sent through the mail in 7-10 business days.