You can create a generalization from the Toolbox, Browser, or Model menu.
Use the Generalization tool in the Toolbox.
Select Model > Generalizations to access the List of Generalizations, and click the Add a Row tool.
Right-click the model (or a package) in the Browser, and select New > Generalization.
For general information about creating objects, see Core Features Guide > The PowerDesigner Interface > Objects.