1. Change settings files.

• Go to <path-to-game>\WarGame\Config
• Open WarCamera.ini
• Find [WarfareGame.WarCameraMode_Default]
• You'll find "FOVAngle=<#>". Change the # to your desired Value of the FOV you want.

2. Through the console

• Open the console "~"
• Enter this code: (set WarfareGame.WarCameraMode FOVAngle <#>) without the (). Change the # to your desired Value of the FOV you want.

3. The FOV for zooming can be changed in the "WarWeapon.ini" file, and denotes the "WarWeapon[Casual/Hardcore/Insane].ini", Each gun must be changed individually.

All these informations were taking from the PCGamingWiki page.