Advice on tracing program logic

Hello

I need a little help working out how to 'trace' a Squeak program.  This is 
the problem which started me off.  I wanted to insatiate a FileList - just 
to play around with it.  I knew I could create one by using the icon in 
the tools flap, but I couldn't work out how to create a new instance which 
was visible. I tried:

tmp1 := FileList open.
tmp1 makeMeVisible

which gave me a debug window.

What I need to understand at the moment is how can I see the code which is 
being called when I click on the File List icon in the tools flap, because 
that is obviously creating an instance in the right way.  I did try 
inspecting the icon but that didn't really give me any clues.

What I am hoping is that if I can understand how an experienced squeaker 
would deal with this very simple case, it will help me understand how to 
learn squeak more generally

Thanks
AB