To use the contents of a RAR file (or its parts), you'll need software capable of extracting or "unrar"ing the files. WinRAR is a popular tool for this, but there are free alternatives like 7-Zip that can handle RAR files among other formats.
Be cautious with RAR files (or any compressed files) from unknown sources, as they can contain malware. Scanning files with antivirus software before extraction is a good practice.
: Only download from reputable sites to avoid malware disguised as data.