Did you buy the download from Costco online? I just helped my friend buy and download it. Her code was on an email. But you got a card? Did you buy it in the store? The card should say how to download it. Maybe this FAQ will help.
How to download Turbo Tax instead of using the CD
https://ttlc.intuit.com/community/installing/help/i-bought-the-cd-but-my-computer-doesn-t-have-a-cd-...
