How to modify Contact form's Input field and Text Area

Hello

I am using t3_bs3_blank template in Joomla 2.5. I want to override com_contact.

I moved files from "/components/com_contact/views/contact/tmpl/default_form.php" to /templates/t3__bs3_blank/html/com_contact/contact/default_form.php

But I cant resize Input fields. How to override "components/com_contact/models/forms/contact.xml" in my t3bs3_blank template????

Any help will be appreciable.

Thanks
Asif