I can’t find the Game folder in my content browser,then I assign another material to my landscape,and I found that something is different between my landscape paint panel and that one shows in manuel.Any one can tell me why is that and where I can find the Game folder ?
Your Terrain actor has a cobblestone material assigned to it that doesn’t support landscapes.
Not just any material can be used on landscapes - you can read this guide on how to create landscape materials: https://docs.unrealengine.com/latest/INT/Engine/Landscape/QuickStart/4/
There is a sample landscape material under Engine Content: /Engine/Tutorial/Landscape/TutorialAssets/Landscape_Material