Hi ,
To get assets from one projec tto another, you can use the migrate feature that describes. In regards to your specific inquiry, the landscape material and the dust are two separate things. The dust is a particle system that you place where you want it and the texture is placed within materials for meshes or in the landscape. The easiest way to find any item you are looking for is to use the filters in the content browser. In this case, filter by particle systems for the dust effect and materials/textures (depending on what specific thing you are looking for) for the . You can find more information on particle systems and materials here:
We also have video tutorials for creating and implementing these here: