Use a tool like WinRAR or 7-Zip . Right-click only the first part ( .part1.rar ) and select "Extract Here". The software will automatically pull data from part2.rar and others to create a single usable .nsp file.
To successfully use this file, you must treat it as part of a complete set rather than an individual file. WOFF-M-NSwTcH-[BASE]-NSP-Ziperto.part2.rar
Ziperto is a well-known site for hosting Nintendo Switch game files, typically for use with modified (jailbroken) consoles or emulators. Use a tool like WinRAR or 7-Zip
The resulting .nsp file can then be installed on a modded Switch using homebrew tools like DBI or Tinfoil. WOFF-M-NSwTcH-[BASE]-NSP-Ziperto.part2.rar