its pretty simple, just open the cheat editor, click on add gamehttp://www.neoseeker.com/Games/Products/DS/dragon_quest_ix/action_replay.html
in this website, you will find game id, which is what you need for the cheats to recognize the games, dragon quest ix is YDQE-23A95403 for US version
then just after clicking add game, put the game title, the game name, in game id, that id, or click on [...] and get the id from the game your using. then click add code, in code title put the name of the code your adding. then go to code list and put the code for it. then choose what button you want it to be activated with and click add, but just once. if you want to add another code, just click on add code. or save, in file ->save->save as type->edge, and there you go.
its easy, and that way you dont need to depend on other people to get your cheats together. just google the "(name of game) action replay codes" and you will have the codes for the game