A quick query- what to do in an interface/main/module .vala file

[arvindpro]

Hi

(1) How to declare the logger in the file with the main() function
(2) How to declare the logger in a file with a module
(3) How to declare the logger in a file with an interface.
I am referring to
private Log4Vala.Logger logger = Log4Vala.Logger.get_logger("ClassName");
(4) Where do I put the config singleton code- just before the main() function? I think that is the right place?

I am sorry if the questions sound silly, I am very new to Vala.

Yours sincerely,
Arvind.