Hi i am using Joomla!2.5 and i had install mobile joomla successfully .
However , the setting of the joomla differs from what is shown on the internet .
So how to i create subdomain using this setting ?
please help .

You don't create the subdomains in the settings, you create them in cPanel (or whatever your host uses).

First step
Create subdomains in cPanel and point them to /public_html/
e.g. m.mysite.com

Second step
Go to Mobile Joomla component. Go to advanced settings. In the area "Subdomains" input the domain you want mobile users to see when they browse the site on their device.
e.g. m.mysite.com

Done.

Potential issues
- htaccess rules may stop or intercept this re-direct. Check your htaccess file to ensure it's not re-directing your subdomain traffic. When I set this up I also had a rule to re-direct all non-www traffic so the mobile subdomain didn't work. I used the following code in .htaccess:
##### Redirect non-www to www -- BEGIN
RewriteCond %{HTTP_HOST} !^m\.mysite\.com [NC]
RewriteCond %{HTTP_HOST} !^www\. [NC]
RewriteRule ^(.*)$ www.%{HTTP_HOST}/$1 [R=301,L]
##### Redirect non-www to www -- END

Hope this helps you.

Hi Thank you for the information . However my Cpanel does not have the features that most tutorial shown . Must i download the Cpanel or it is by default . j3 is a picture of my Cpanel .
I am using at a localhost , will this be one of the problem to creating a subdomain for mobile joomla ?

Hey Terence, the image you attached is not cpanel, that's Joomla admin. If you Google cpanel you'll see what it is.

If you're just creating this on your localhost there really isn't a need to go through the complex process of setting it up on a local subdomain. Once you launch your site then revisit this post if you wish to set up mobile joomla on a subdomain.

Thank you once again . We are working windows 7 not linux enviorment . does it have any issue with the Cpanel . do you have any link to downloading cpanel for free ?

Terence, you don't need cpanel, it's not for local development.

im so sorry but im still confused. erm. if you dont mind. could you please guide me from the start. .

ok. i have Joomla2.5 installed.
i downloaded a file "Mobile-Joomla.1.0.3.1.tar" and i installed it by uploading it into the extension manager. 
so what is next step to do to complete the configuration ? like what do i have to fill up

i have this actually.

There's loads of information about initial set ups, try searching this site, this forum, Google, etc.

www.mobilejoomla.com/documentation.html

www.ostraining.com/blog/joomla/mobile-joomla-tutorial/

Good luck!