Hello welcome to the forum.
There are a number of tutorials on http://www.gtk.org/documentation.php
which should help guide you on your way. The page you link to shows a simple setup that can easily be done with a hbox (and maybe a bit of formatting if the borders are what you want).
The tutorials are written for gtk2, whereas gtk3 is the current version. There is, however, very little difference as far as a beginners tutorial goes and you'll probably find it useful no matter what version (!=1) that you are using.