3D Warehouse is easy to find. You can always go to https://3dwarehouse.sketchup.com/ in your preferred web browser, or just look for the 3D Warehouse icon ().
SketchUp for Desktop
In SketchUp for Desktop, you can find 3D Warehouse in the Getting Started, Large, and Warehouse toolbars.
SketchUp for Web
In SketchUp for Web, you can find 3D Warehouse on the right side among the Panels.
SketchUp for iPad
In SketchUp for iPad, you’ll see 3D Warehouse at the top of your Main Toolbar.