First code always listed will be a master code which you use first. Once all the information is put into the Master Code area you then Ok that and it will be saved.
Now you can put in your other codes, do refer to instructions on how they work.
If the codes don't require a Master Code then it is ok you can use whatever codes you can.
The only real ones I have seen so far is the ones listed here on the site.
www.cheathappens.com/show_cheat.asp?ID=25338 (basically a copy of the ones listed on AR's own site)
Other fan based codes can vary, as others will be making up the codes from other cheat device codes and converting them which are not a 100% guarantee to work, or people using a DS emulator to play roms and trying to convert normal addresses to AR codes.
[Edited by DABhand, 12/1/2010 1:10:02 AM]