[Gtk2] ocamlmktop?

I try to work with the examples of the LiblGtk2-Ocaml
(Ocaml-Gtk2-Bindings).

But of course they don't work because of missing/unloaded libs/moduls.

# #use "hello.ml";;
File "hello.ml", line 12, characters 0-10:
Error: Unbound module GMain

I know ocamlmktop but don't know how to use it here. What do I have to
load here? Shouldn't hello.ml take care for itself of the correct
loaded modules/libs?