In case you are using the app:
- Click on My Collection and click on Redeem Code.
- Simply enter your game key in the activation field and click Next. Make sure that there are no spaces left before or after your code.
In case you're activating the product key on the EA website:
- Log in and go to your Account Settings page.
- Click the Redeem Product Code button on the left side of your screen. Enter your key in the activation field and click Next.