Right-click only on the first file ( .part1.rar ) and select "Extract Here" (or "Extract to...").
Ensure tramsim_vienna.part1.rar , tramsim_vienna.part2.rar , and tramsim_vienna.part3.rar are all downloaded into a single directory. tramsim_vienna.part3.rar
Note the installation path and version numbers. Right-click only on the first file (