Assets and Scene Tabs
The Assets tab lists all assets that can be used by the project. You can import assets several different ways:
Once a model is imported, you can drag it into the Storyboarder to use it with other nodes, most likely to initialize it in the Setup Node.
Scene Hierarchy Tab
The Scene Tab lists all objects in the Editor. You can drag objects from here to the Storyboarder tab. Selecting an object in the tree will highlight it in the Editor.
Next: Properties Tab