In soulsilver? Easy. First, you need to beat the Elite Four 200 times without turning off your game then you talk to Professor Oak with Articuno, Entei, Moltres, Raikou, Suicune and Zapdos (in that order). After that he will give you a rainbow Apricorn and you give it to Kurt and he will make you a Master Ball (important!!) you then need to complete the normal pokédex and Beat Red 6,000 times in total and you go to where you got your starter pokémon and there will be 3 pokemon in pokeballs. If you chose Totodile, you get Kyogre, Cyndaquil, you get Mewthree :) and for Chikorita you get Shaymin. If this doesn't work reboot your game and try again.
Ok then, try it out!
Ok then, try it out!