When you create a new diagram, the Diagram View presents an empty background. You place the various model elements on the background and draw relationship links between them according to the requirements of your model.

1. In the Model View, right-click the target project.
   Tip: Alternatively, you can use the shortcut CTRL+SHIFT+D
   .
2. Select the target namespace (package) either in the Diagram View or in the Model View. If you do not select a custom namespace (package), Together adds a new diagram to the default one.
3. Choose AddOther Diagram on the context menu.
4. In the Add New Diagram dialog box, choose the Diagrams tab.
5. Select the diagram type.
6. In the Name field, enter a name for the new diagram.
7. Click OK.

Result: The new diagram opens in a new tab in the Editor Window. You can use the Object Inspector to view and edit the diagram properties. 

To create a new diagram, use can also use the HyperlinkTo New diagram command on the context menu of the Model View or the Diagram View. 

You can create a new logical class diagram using the context menu of the root node for your project, or by using the context menu of a namespace element in the Model View. Choose either AddClass Diagram or AddOther Diagram. Choosing the latter command opens the Add New Diagram dialog box. When you place a class, interface, or namespace on a logical class diagram, Together generates the corresponding source code or descendent namespace in the namespace where this class diagram is located.