Right-click part1.rar and select "Extract Here" (this will automatically pull data from part2.rar ).
Ensure you have all .rar files (part1, part2, etc.) in the same folder. Song.of.Horror.Episode.5-CODEX.part2.rar
Mount the resulting .iso file using a virtual drive or extract it. Install: Run setup.exe and follow the prompts. Right-click part1
Copy the contents of the CODEX folder from the ISO and paste them into the game’s installation directory (overwrite existing files). Play: Run the game as Administrator. Song.of.Horror.Episode.5-CODEX.part2.rar