Once you activate your FF Diamonds, they should appear in your account in just a few moments. 

You will also receive a confirmation email on your email address after successful activation.

In order to activate your product on the Xbox website, you will need to login into your Xbox account: If you choose to redeem your key directly through your Xbox console then login to your account, then:

In order to redeem a PSN key you can do it both Online and through your console. If you chose to activate the key through Playstation website then sign in to your account, then: If you chose to activate the key through Read more…

You can activate your Game Key on Origin either online, or by downloading the Origin client for PC.