I am not able to setup Gmail Mail account - error shows wrong user name or password, where as I am inputting correct password and IMAP Setting.

This error will occur if you have two factor verification enabled on your Google account. In this case you will need to generate an "Application Specific Password" (see https://support.google.com/accounts/answer/185833?hl=en) and if you don't want to re-enter it every time you wish to retrieve or send messages use the Thunderbird Password Manager to save it (but don't forget to set a password for this as a security measure).