How do I enter the cheats for Action-Replay?

You must have the Action Replay Cheat device..enter the master code first then your specific code...

You need an Action Replay first! You can get them at game stores or Walmart for $20-$25. It will have some codes preloaded, but if you want to put one in, then you go into Add/Edit Game, then Add/Edit Code, then if the Master code matches then just name the code and put it in. If the Master Code doesn't match, make it a different game(Like Emerald 2 or whatever it's a code for)or enter the other Master as Master Code 2, but you need to remember which to use with which codes, so a different game name might be easier to use. Also, often there are 2 columns of codes the way they list them, do not go down the one column, then the next, go from left to right, then go down to the next line-this can be confusing sometimes. And whatever you do, be careful, don't use too many codes at once(more than 1 or 2 is risky depending), especially encounter codes as they won't work that way. Other codes to be careful with are ones that give you All Key Items-no room, All Balls, or any other code that gives you infinite anything as it takes up a lot of memory and you can't get rid of it all, ever! Walk through walls codes are silly and dangerous, too, as are some complete Pokedex codes. Also, always check to see what you've done with your code before saving, because once you save you're stuck. Enjoy, but be careful, OK.