Many RAR files shared privately are password-protected. You will need to get the password from the person or site that provided the link.
A free, open-source alternative that supports RAR extraction. Download RLFFbks12RD rar
Once you have the software installed and the file downloaded: Many RAR files shared privately are password-protected
Only download from sites you trust to avoid malware. Download RLFFbks12RD rar
Available on the Google Play Store for mobile extraction. 3. How to Extract the File