Thank you Ixian.
Here is what I’ve done so far.
1- Created the website
2- Registered with google webmaster tools
3- Received an HTML file, uploaded in my root directory. As it is requested by google, it’s viewable on http://www.mysites.com/googlefile.html.
4-I went back to webmaster tools and clicked on Verify my site. I received the error message that I’ve given earlier. ( I have about 7 websites and up to this point all websites are verified without uploading site.xml)
5- I use joomla template and it has an extension component to create site map which is called joomap. Using this component, I created a Sitemap.
6-I copied my sitemap link and pasted into Site map url in Webmaster tools. The error message is still there.
I thought maybe this component is the problem so I found below link on google to create XML
http://www.xml-sitemaps.com/
I created a Site map using this, (It found 13 broken links but I dont think this should be a problem to verify my site) and paste the URL in webmaster tools.
The error msg is still there.
If the solution is creating a Sitemap along with uploading google html file, I am happy to use any Sitemap software. I appreciate if you could advise me on that. Thank you!