Email for gift card sends me to install itunes (already have it)

I recieve a gift card via email which has the only option of a "Redeem Now" button. When I click the "Redeem Now" button I am brought to a window which prompts me to download iTunes. I already have iTunes on my computer and have had it for several years. I did go ahead and download it to see what would happen and all it did was "repair" itunes. What do I need to do to get the gift card?