Where do you go in Pokemon SoulSilver to transfer Pokemon to Pokemon White?

You don't do anything on SoulSilver itself. On the Pokemon White game, go to the PokeTransfer lab and start the transfer. On the other DS, with SoulSilver inserted, go to Download Play from the DS main menu (not SS's main menu or in-game menu). After following the onscreen instructions, you'll be able to migrate some Pokemon.