Creating Elements
With UModel, new elements can be created as follows:
•From the Model Tree window. With this approach, elements are added to the model only, and you can insert them later into diagrams if necessary.
•From any diagram window. Any elements added to a diagram are also automatically added to the model as well. Should you need to delete an element later, you can choose whether it should be removed from the diagram only, or deleted from the model as well.
To add elements from the Model Tree window:
•In the Model Tree window (or Favorites window), right-click the element (for example, package) under which you want the new element to appear, and select New Element | <Element Name> from the context menu. For example, to add a new package under the "Root" package, right-click the "Root" package, and select New Element | Package.
To add elements from the Diagram window:
1.Create a new diagram (see Creating Diagrams) or open an existing one (see Opening Diagrams).
2.Do one of the following:
a.Right-click inside the diagram and select New | <Element Name> from the context menu.
b.Click the toolbar button of the element you wish to add, and then click inside the diagram. To insert multiple elements of the same type, hold down the Ctrl key before clicking inside the diagram.
Packages
As you model elements, you will likely need to work with packages more often than with other elements. Each entry marked with a folder symbol 
in the Model Tree window represents a UML package. Packages in UModel serve as containers for all other UML modeling elements (including diagrams, classes, and so on) and have the following behavior:
•They can be created at any position in the Model Tree.
•They can be moved or copied to other packages (as well as into valid model diagrams), see Renaming, Moving, and Copying Elements.
•They can be used as source or target elements when code is generated or synchronized with the model, see Forward Engineering (from Model to Code) and Reverse Engineering (from Code to Model).
When you create a new UModel project, two packages are available by default, the "Root" and "Component View" packages. These two packages are the only ones that cannot be renamed or deleted. The "Root" package serves as starting point for modeling all other elements, while the "Component View" package is required for code engineering.
Default UModel packages