Create a DefaultGameUserSettings.ini file in your Config folder and set variables as you want:
[/Script/Engine.GameUserSettings]
bUseVSync=True
ResolutionSizeX=1920
ResolutionSizeY=1080
LastUserConfirmedResolutionSizeX=1920
LastUserConfirmedResolutionSizeY=1080
WindowPosX=-1
WindowPosY=-1
bUseDesktopResolutionForFullscreen=False
FullscreenMode=0
LastConfirmedFullscreenMode=0
Version=5
above settings will give you 1920x1080f with VSync enabled.
PS: But I would recommend you to set it in code after checking DisplayMetrics to make sure the display supports specified resolution.