If you go to the AR Codes FAQ under pokemon emerald cheats it has all of the codes for action replay.
at the startup screen of the AR, you should have an option to play the game, settings, and something else. choose something else. it should come up with a big list of games. if the game is not there, make one. if it is, click "a" on the game. it will then come up with the cheats for that game. if the cheat isnt there, go online and click enter cheat on your gameboy. you will now have a place with a couple of underscores that you can enter letters and numbers on. when you are on dthe cheat site, enter the code shown into the underscores. then click enter. you will then name the code. name it whatever you want. select the code, and play the game. if you are still confused, read the directions and they will tell you what to do.
All times are (GMT -06:00) Central Time (US & Canada). Current time is 11:20:36 PM