to check and see if your game has any codes; right click on the game in the start up menu for dolphin, where you see the games listed out, and click on properties.
a new menu with several tabs will pop up. two of those tabs are ar codes and gecko codes. the ar one should already have codes listed if any official ones already exist. the gecko codes tab has a download option, which will have dolphin check the database [i think it has one. i have no idea what it checks, but it checks something and grabs the codes from there] and add in any codes that it finds there.