In the stats panel, click the Materials link. You then see a list of the materials along with a bit of info about each one, as shown in the following figure.
When you find a material, click the Download link.
If you accessed 3D Warehouse from SketchUp 2017, SketchUp then retrieves the material from 3D Warehouse and activates the Paint Bucket tool with the material loaded and ready to go. Click on the surface that you want to apply the material to, and, you’re done!
If you accessed 3D Warehouse through a web browser, the SKM file for that material downloads. You can then add the SKM file to your local SketchUp content folders.
To see the Materials feature in action, check out the following video.