Placing objects

When you first create a scene, it is empty. To add something to it, use the asset browser at the bottom. In the asset browser you can find not only your own imported assets but also some assets that exist by default such as shapes. Select shapes in the asset type selection box on the top to the left in the asset browser. Then click on one of the shapes and then click "Add to scene". Move your mouse to the scene and click your left mouse button to place the shape in your scene.