Adding apps to the main menu...?

["Thomas Tschoepke S." <ttsoares orion ufrgs br>]

Sorry this lamer question but, how could I edit the main menu tree...?

With KDE it was an easy task but with Gnome is not so intuitive, from me
  at last ;-)

TIA!
-- 
|Porto Alegre| Thomas Tschoepke Soares        |     //   Mate do
| RS - Brasil|   ttsoares@cedep.ifch.ufrgs.br |(~~~//'~)   estrivo
bendito
|---------UIN:961141--------------------------| \     /  Amargo que 
| The fact is a secondary aspect of reality   |  `\_/'     a gente
bebe...