Just click this link. It's that simple. After you've done that, follow the instructions below the break to redeem your code.
1. Download and Install Dizzel through Steam
2. Once in-game, locate and click the 'Shop' button on the top menu.
3. Press the 'Cash Reload' button located on the bottom right.
4. Steam's Cash Purchase window will be displayed.
5. You will notice 'Item Package Redemption' on the right section.
6. Please input your Keycode, and press 'Redeem.'
7. Please allow up to 15 minutes for delivery. Your item will arrive in your Inventory's 'Storage' section.