Pokemon platinum how do you get in Pal Park?

after you get the national pokedex, you need to insert a GBA game like firered or leafgreen, in the start menu, you choose migrate from GBA or migrate from "choose the color of the game (leafgreen, firered, ruby,...)". Then you choose six Pokemon from the GBA game, you'll transfer them to platinum. Carrying these Pokemon, you'll be able to enter pal park and catch Pokemon in various locations.