You can create an interface in any of the following ways:
Select the Interface tool in the diagram Palette
Select to access the List of Interfaces, and click the Add a Row tool
Right-click the model or package in the Browser, and select
Right-click a class, and select Create Interface from the contextual menu (this method allows you to inherit all the operations of the class, including the getter and setter operations, creates a realization link between the interface and the class, and shows this link in the Realizes sub-tab of the Dependencies tab of the interface property sheet).
For general information about creating objects, see the Objects chapter in the Core Features Guide.