Im not exactly sure, probably through Bluetooth. Theres a button in the app that says import bin file. You tap that then find the place on your phone or in cloud (I use google) where the files are stored then choose the file for the villager you need. Each one has the name and amiibo card # of villagers so its easy to find. Also, Nookipedia has the amiibo card list so you can just use the find on page function in your browser to find the series & card number you need. Once the correct villager is located in the app, tap it, then tap save. Youll go back to the main screen and tap write to NFC tag then hold the device up to your phone and itll add it to the device! Then you just scan it like a normal amiibo on the right joystick on your switch at the resident services Nookstop after choosing the option to invite a villager.