In houses in rustboro city, pacifidlog town, fortree city.
You can find people through the map who want to trade Pokemon with you.
trade
Trade from Emerald
Trade it from pokemon ruby
You can do this after you find the Ruby and the Sapphire for Celio in Pokemon FireRed. then you can trade with Ruby, Sapphire and Emerald.
Common places to find the in game trade trainers: Houses, Buildings, Mart's, Special Area's.
You can't get ekans on emerald trade one from firered.
you cant catch mewtwo in Pokemon emerald. to get it you must trade with either Pokemon firered or leafgreen.
You must trade it from Emerald.
Trade it from other games
you trade from emerald
You'll need to trade for it.