Hello Magicboy926,
The reason that you are seeing him paint and the ground is not raising up is that he is in paint mode. This allows for you to paint your material over the landscape in your scene. If he were still in sculpt mode then the landscape would still rise. So, while in sculpt mode, depending on the strength/falloff/ and size of your brush you are able to manipulate the landscape by various values. If you click and hold your mouse you will see the landscape rise based on the previous mentioned parameters. Since these calculations are vertex based you are able to click and drag to influence the area where you brush interacts with the landscape. Clicking and dragging over a part of the landscape that is already raised will calculated the already risen landscape as a default value of 0 and will continue to add on top of whats there.
I hope this helps shed some insight to the landscape and it’s tools. Here is a link to our documentation on landscape tools that should explain in greater detail what the tools are and how they function.
https://docs.unrealengine.com/latest/INT/Engine/Landscape/QuickStart/1/index.html