Packages

A package partitions the domain and the associated work. It is used to organize elements into groups, particularly use cases and classes. Packages may be nested within other packages. Packages are linked by contractual relationships that define their interface.
Examples of packages: the commercial information system, accounting, production management, digital control of a machine, an alarm system, etc.
You can create a package using the

button in the toolbar. You can then increase its size in order to place use cases within it.
You can link a use case to a package simply by placing it within the package. When you have moved the object within the package, the package shape is highlighted to indicate that the object will be connected to it