So, you have an EveryDollar Plus account. To redeem your voucher, start by looking in the bottom left corner of the screen where you should see a "Settings" icon. It looks like a little cog or gear. When you click on that, it will take you to your Settings page.
On the Billing page, you should see a section that says "Got A Voucher?" Click "Redeem Your Voucher".
Enter your Voucher Code and click "Next".
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 page.
Now just fill in your payment info, click "Redeem Voucher", and you're all set!