Windows in separated packages. How?


I am learning is the Vaadin. I made an application with login window and a main window, which contains a menu. The menu can be opened in different windows. If the same file prepared by the windows, everything is working properly. But I want to be put the windows into different packages. But I do not know how should be called the windows in this case. Is it good or completely bad idea to go through? Could anyone advise me or a good description, an example that i can follow the logic?

Thank you!

I have found the answer in
this chapter