The Selector Tab

Select an object or light by clicking on it's name in the tree control.

Add a light to the scene by clicking on the Add Light button.

Add an primitive object by clicking on the Add Object button.

Copy (Duplicate) the Selected Object by clicking on the Copy Selected button. Note that the copied object will become the selected object, and will be positioned directly on top of it's source. Move the copy to see both the source and it's duplicate.

Delete the Selected Object by clicking on the Delete Selected button.

Change the size of the Scene window by entering the exact Width and Height in pixels.