Xcode Launch Screen Storyboard

I imported my game from a third party platform that uses splash screens opposed to launch screens. Now that I'm working solely in Xcode with my game, I'm trying to create a launch screen. I see that Apple asks for a launch screen storyboard rather than static images, but I'm confused about how to do this. I created the storyboard, and I can figure out how to get images into the storyboard, but I can't figure out how to make the image adapt to all device sizes.

What size should my image be? How do I make the image scale for all devices from the iPhone 4s to the iPad Pro 12.9?
Any advice having to do with any of this would be greatly appreciated.

Thanks so much!