Need help to understand how to work with tkd

[Suliman via Digitalmars-d-learn]

Now I am trying to learn how to build GUI apps in D. But I have 
some troubles.

http://code.dlang.org/packages/tkd

1. I can't understand how to set window size in example on page 
above. I looked at docs and found only how to create new window. 
But here I do not see any procedure that create window and set 
it's params. I see only initInterface.

2. Do I right understand that all GUI stuff should be placed only 
in:
class Application : TkdApplication

3. I need to get file name from dialog and use it's for example 
in main
	override protected void initInterface()
	{
...	
string fileToOpen = dialog.getResult();

	}

How I can get fileToOpen from main or another instance. Could you 
show example?