[plt-scheme] Debugging servlets in DrScheme

I decided to have a look at DrScheme enviroment and test servlets
teachpack hoping that I can interest some kids (8-9 grade) to play
with it, maybe build some kind of interactive fiction story or
something like this. I heard that it is possible and quite easy to
debug servlets in DrScheme and my understanding was that when you type
something like

(inform "Hey!")

a browser should start with a simple page generated by servlet.

I spent few hours reading docs, googling, etc but I have no idea how
to do it. DrScheme just has ladybug  symbol and paints inform with red
color without explanation of any kind. What kind of magic incantation
I am missing? What language, teachpacks (except for servlets2.ss)
should I choose? Or have I misunderstood tutorials completely? If yes,
what should  do to start web server? Is there some magic address I
should type into browser? I see a lot of examples on web and in
DrScheme documentation, I just have no idea how to run them....

I use DrScheme 352 in Ubuntu. I have only couple of hours experience
with DrScheme but quite confident with simple Common Lisp (Practical
Common Lisp by Seibel and slightly more, including its allegroserve
examples).

Thanks!