There are a few ways to get Call of Duty Modern Warfare for free on PlayStation 4. The first way is to purchase the game digitally from the PlayStation Store. The second way is to sign up for a PlayStation Plus account and receive a code to redeem for Modern Warfare for free. Finally, you can also purchase the game through Amazon.com or other online retailers. To get Modern Warfare for free on PlayStation 4, first make sure that you have an account with Sony Interactive Entertainment America (SIA). Once you have an account, sign in and click on the “Games” tab. Under “Games,” click on “Call of Duty: Modern Warfare.” If you don’t have an account yet, create one now and add Modern Warfare as a game title. Once you have added Modern Warfare as a game title, click on the “Redeem Code” button at the bottom of the page. You will be asked to enter your PSN ID and password. After entering these information, click on the “Redeem Code” button again and confirm your redemption by clicking on it. You will then be taken to a page where you will see your code in red text. Copy this text and paste it into your PS4’s console settings so that you can easily find it when playing Modern Warfare online or offline. If all else fails, you can always try purchasing Modern Warfare through Amazon or other online retailers instead of Sony Interactive Entertainment America’s website.