Use Tinfoil, DBI , or Awoo Installer to install the base game first.

Right-click the .rar file and extract the contents to your PC. Transfer: Move the .nsp files to your Switch's SD card.

Switch Tutorials #2 Installing Games (.XCI .NSP) Game Card Backups

Ensure your Switch is running the latest Atmosphere or equivalent custom firmware.

NSP files are optimized for digital use and take up less space than XCI cartridge dumps.