Ok first make sure that u always have both devices, then u must go in Pokemon go settings and scroll till u see Nintendo switch then press it and well just connect to a Nintendo switch then go to fuscia city and go in the place with all the Pokemon (or just go to a random building until the Pokemon go muziek plays in one of them then go in Pokemon lets go pikachu options and tap Pokemon go settings then will ask u to do a lot of Pokemon Link stuff *blah blah blah* then it will say "ThatOneGuy's account was found do u want to access it then tap yes then u go to Pokemon go and go to your Pokemon and click that Nintendo switch on the top, boven right of your application and select the Pokemon u want to transfer then go back to the game (Pokemon Lets go pikachu)and to the man on the top, boven left and go to bring Pokemon then your Pokemon will pop up in a go park and it will toon the amount of Pokemon u transferred then go to the Pokemon park and catch the Pokemon there (If it is a starter of an evolved Pokemon I definitely reccomend bringing great balls+ and razzberries+ and Silver Nabnab berries) But if it is a really strong Pokemon it will only be 1/3 of 1/4 of its original Combat Points but still hard to catch (Ive transferred my Charizard 2000CP and it turned to 500CP as a lvl 20) It might be a low level but I recommend grinding on route 5 -7 its great for lvl 20's! Oh don't worry when the Pokemon run away it just appears right in front of u again
