Not able to install module using Plugin Manager / How to Set FTP details in the Plugin Manager.

I have installed drupal-6.20 and have installed Plugin Manager module successfully.

I am trying to install quiz module using this Plugin Module, but am receiving an error
while drupal is trying to install the Quiz Module in /sites/all/modules/ folder.

Home › Administer › Plugin Manager - Install

Installation method: FTP
Hostname: localhost / OR / ftp.domain.com / OR / domain.com
Username: FTP Username
Password: FTP Password

Click - Install - Button

Received ERROR - Could not login to the ftp server.
Unable to install quiz.

The username, password are the same as used successfully in FileZilla FTP Software.

Also, how to ADD the details from successful login to the Plugin Manager.
I have not set any FTP details in the Plugin Manager.

Please guide me to remove this error and install the module successfully.