After starting application first time, dialog window appears, with message:
"There are no connections currently configured - do you want to create a new connection?"
It is possible now to create first connection and connect to database. 

Read more: Connection configuration.

Application window starts maximized. There is possible to resize the window and its components, and store this layout settings via: second button in toolbar - Save layout or via menu: View: Save layout. Next time, the application starts, will keep the preferred window and components size.