B4J Question change screen b4j

hi i use b4a

I'm starting in b4j, but I do not understand how to move from one screen to another.

I create another screen called "main menu" and it only says:

'Static code module
Sub Process_Globals
Private fx As JFX
End Sub


the other thing that I do not understand is how to change the screen in b4a is simple ..

StartActivity ("screen")

but in b4j how is it done?

thanks for the orientation