Select the Nintendo DS Pokémon game you wish to start from the home screen.
Using a Nintendo DS system with a GBA cartridge slot, insert your compatible GBA Pokémon game (LeafGreen, FireRed, Ruby, Sapphire, Emerald) along with either Diamond, Pearl Platinum, HeartGold, or SoulSilver into the DS slot.
How to transfer Pokemon from Game Boy Advance to Pokemon HOME Ruby/Sapphire/Emerald: Lilycove City in a house east of the Department Store.LeafGreen/FireRed: Fuchsia city in the house next to the Pokémon Center.Pokémon with hidden moves like HMs (surf, cut, fly, etc.) cannot be transferred, so you'll need to go to the Move Deleter first and make the Pokémon you wish to forget any HMs they know. To transfer many of these Pokémon, you'll need to ensure you've unlocked the National Pokédex in the aforementioned games you are using.
You will also need a 4th (Diamond, Pearl, Platinum, HeartGold, SoulSilver) or 5th (White, Black, White 2, Black 2) generation DS game and an older Nintendo DS that has a Game Boy cartridge slot. Note: Only Pokémon from LeafGreen, FireRed, Ruby, Sapphire, and Emerald can be traded. Transfer, trade, and store: Pokémon HOME (Free at Google Play).3DS storage: Pokémon Bank (Free trial at Nintendo eShop).Sinnoh: Pokémon Diamond ($40 at GameStop).The original Kanto remake: Pokémon LeafGreen ($45 at GameStop).Get 'em to HOME: Nintendo 3DS ($130 at GameStop).Transfer those GBA games: Nintendo DS Lite ($55 at GameStop).Fear not, though, because it is possible, and you'll have your favorite GBA Pokémon into Pokémon HOME soon enough. Still, it is a long and tedious process that requires a couple of different Nintendo DS systems to be on hand. Transferring Pokémon from your Game Boy Advance (GBA) games to Pokémon HOME isn't necessarily difficult.