How do you get mew through mystery gift?

Answer 1

On certain Nintendo events (listed on Pokemon.com) you will get an old sea chart as your gift. Go to Slateport city and inside the port show the ferry guy the chart Mr. Briney will come out and take you to faraway island where you will find mew!

Also action replay has a code but I don't know it

Answer 2

Mystery Jungle is 30 floors long (29 floors and the boss floor, which is Mew). To recruit Mew, make sure that you only bring 1 or 2 Pokemon with you so that you have room to recruit Mew. If you have 4 Pokemon in your team or the size factor for all of your Pokemon is more than 6 stars, you will be unable to recruit Mew. Also, when battling Mew, in order to recruit Mew, you have to make sure that your leader is the one that defeats Mew, and you must defeat Mew while you are standing within 1 tile of Mew. If you defeat the Mew in any other fashion, you will NOT be able to recruit Mew. You must have the dungeon mystery jungle in order to get mew and you must have beaten blizzard island in order to get the secret rank from scizor. The wondermail code is x%8s wyy+ s-jf pfh@ @##k 5w8k