Hi Sarang Mehta,
The .qar file format is associated with QlikView and will automatically install the Extension to the correct location. However, to install the .qar file on a server must be set up manually. The steps are simple.
1. Rename the .qar file to .zip
2. Unzip the file
3. Place all the folders in a location equivalent to "%ProgramData%\QlikTech\QlikViewServer\Extensions\Objects\"
If you do not see necessary folders, please create them accordingly.