Company selector in main window


I am very new to Cuba and to Java development and I have a question.
I need to have a company selector in my main window. It looks like lookup field might be a good choice. It will take Option values from Company datasource. When the user selects the company it must be stored in Session attribute. if the user refreshes the window, the company from a session attribute must be selected in the dropdown.

Could somebody advise me what might be the best solution to achieve this.

Thank you

Studio provides means to extend Main and Login windows, so you can customise them in any way you want.