> I searched the forum but couldn't find an answer
> that works for my question.
You didn't try very hard. 
If you searched for PASSWORD you would have easily found (amoung countless)
Re: Copy files from password protected sites -
<http://forum.httrack.com/readmsg/16034/16032/index.html>
If you searched for PROTECTED you would have found (amoung countless)
Re: How to capture URL requiring USERNAME and PASSWORD -
<http://forum.httrack.com/readmsg/20890/20883/index.html>

> password protected site.  I want to download using 
> httrack username:password@www.xyz.com 

Does your site use http protection or a form. That's for http.