You can create an object node in any of the following ways:
Use the Object Node tool in the diagram Palette
Select to access the List of Object Nodes, and click the Add a Row tool
Right-click the model or package in the Browser, and select
Drag and drop a classifier from the Browser onto an activity diagram. The new object node will be linked to and display the name of the classifier.
For general information about creating objects, see the Objects chapter in the Core Features Guide.