Spend Cards may be upgraded through the Spend Wallet/Spend App. Users whom have acquired more Spendcoins and want to utilize the upgrade process may do so directly within the app.
To upgrade your card:
Click on the "Card" tab at the bottom of the app
Once in the card section of the app click on the "settings" wheel at the top right of the screen as seen below
Once in the "settings" menu you will be able to select the option that says "Upgrade Card"