You can add and delete objects in the Environment using menu commands or tools.
Do one of the following:
Choose an object type from the New menu in the Environment menu bar.
The object is added to the current layer.
Click a layer background with the Pencil tool.
A new instrument object is created.
Do one of the following:
Select all objects you want to delete, then choose Edit > Delete in the Environment menu bar (or press Delete).
Click the object with the Eraser tool.