: The .nsp is currently packed inside a RAR archive to reduce file size for sharing. You would need a tool like 7-Zip or WinRAR to extract the actual game file.
: This is a Nintendo Submission Package . It is the digital format used for games on the Nintendo eShop. RAILGRADE [0100F2C0181C4000][v0][US].nsp.rar
: These files are typically used with Nintendo Switch emulators (like Ryujinx or Suyu) on a PC, or on a modded Nintendo Switch console. RAILGRADE [0100F2C0181C4000][v0][US].nsp.rar
If you are looking for a "helpful guide" on how to actually the game once you have it running: RAILGRADE [0100F2C0181C4000][v0][US].nsp.rar