If you are playing on an emulator, the process involves "installing" the file to the virtual NAND.
For players installing this specifically for the content, the 2.20 update (and the surrounding Purapura patches) was significant because it: yokai watch 4 purapura nspatualizacao 220 install
Highlight the icon on your Nintendo Switch HOME Menu. Press the + Button to open Options. If you are playing on an emulator, the