To migrate Pokémon you must first have access to the Pal Park in Fuchsia City of Kanto (this is when you have the menu option before loading the game). This will be located in the area where the old Safari Zone used to be located in RBYG/FRLG. Like in DPPt, the Pal Park works exactly the same. However, they expanded the feature in which it does not limit you to six Pokémon per day for each Pokémon GBA cartridge like before in DPPt.
Note, only the Japanese version FRLG/RSE will work with the Japanese version HG/SS.
For future reference though, you may use the
HG/SS Help Thread for simple questions on the game. :D