How do you do action replay for ds?

To use your Action Replay DS, you insert it into your Nintendo DS and place the game you want to "cheat" for inside the Action Replay. You then turn on your console, and it should bring you to the main Action Replay Screen. Click on the Star "*" in the corner of the screen to go to the games list, or the game that is inserted in your Action Replay.

From there you can add codes. You can get codes on many websites, like Codejunkes.com or WARC.us. You then type those codes in on your DS, or you can use your computer.