Was just looking at FIFA 15 and this was the cheapest I could find for PS4.
Since this is US PSN store, you must have a US account for PSN. It is not hard to create one.
After that, you must buy either 1 x $50 or 2 x $20 PSN vouchers. To buy these, you must have a US amazon account and you must enter a US address. Don't worry though, the code is digital so it will be sent to your email.