In order to use the item editor, follow these directions.

1) Open up database.tpl in 'Nightmare.exe'.
2) Open up the item editing module with nightmare.
3) Edit what you want, hit enter after making changes to an item, and after you are all done,
hit ctrl+s to save.
4) Use NLZ77 Compressor and recompress the files following the tutorial included with it.
Thanks to Nintenlord for the program.
5) Put the file "database" in the "data" folder of your decompiled NDS ROM. Make it replace the old one so that the new changes replace the old data.
6)Recompile the ROM using DSLazy or another program of your choice.
7) Test the game to see if your changes work. 

Contact at smashfire17@gmail.com or http://www/feshrine.net for help and more info.