1. Click "Settings" in the bottom left.
2. Click "Redeem Your Voucher".
3. Enter your Voucher Code and click "Next".
4. Read the Billing Cycle info. This section informs you that you will be charged at the end of your voucher term unless you turn it off in your settings.
5. Now just fill in your payment info, click "Redeem Voucher", and you'll be good to go!