Here's the instructions on how to redeem it and my code(not sure if it's all unique codes being sent out or just the same code to everybody). Please post when you've used it so no one else wastes their time. Thanks.
Follow the instructions below to redeem your code:
1. From the HOME Menu on the Nintendo 3DS™ system, select the Nintendo eShop icon
2. Select "Settings/Other", then select "Redeem Download Code"
3. Tap "Enter a download code"
4. Use the touchscreen to enter the download code and tap "Ok"
5. Tap "Ok" again
6. Select "Download Later" or "Download Now"
Items downloaded now will begin immediately. Items downloaded later will begin when the system enters sleep mode or while browsing the Nintendo eShop.