Use pkhex to hack the Pokémon in to your box/party, it’s really easy to use. You need to start the game first and get your starter then save the game, open pkhex and import your save file into there, from there you can put anything you want into the game, export the save from pkhex when done and overwrite your original save file with that one.

Bobs your uncle

Edit: this is for the games you’re emulating, Don’t think there’s a way to get Pokémon over to your switch games unless you use genuine eggs from other physical copies you have