After you purchase your EA Card go to the Store on this website and click the amount of Cartel coins you would like to buy.
Under Payment Options there will be a section Called "EA Account Balance" choose that.
From there, click the yellow Hyperlink that says "Redeem an EA Game Card". You'll be prompted to enter in your code, no spaces.
Once it's entered you'll be able to complete your transaction.
Thank you very much!