Opening the JPA Diagram Editor
In the Project Explorer, select the project that you want to use for your entities.
From the project context menu, choose JPA Tools → Open Diagram .
Creating New Entity
In the Entities list of the Palette, choose 
(Entity), and then click upon the diagram
area.
The Eclipse IDE creates the new entity with a predefined name and a primary key.
Creating New Embeddable
In the Entities list of the Palette, choose 
(Embeddable), and
then click upon the diagram area.
The Eclipse IDE creates the new embeddable with a predefined name.
Creating New Mapped Superclass
In the Entities list of the Palette, choose 
(Mapped Superclass), and then click upon the
diagram area.
The Eclipse IDE creates the new mapped superclass with a predefined name.
Displaying Existing Persistent Types within a Project on the Diagram
To display a single persistent type, copy the persistent type, using drag and drop, from the Project Explorer to the JPA diagram.
To display all persistent types, click on the JPA diagram with the secondary mouse button and choose Show all Persistent Types. The alternative way is to copy the JPA Content node from the project, in the Project Explorer, to the JPA diagram, using drag and drop.