Adding New css file in IP2013

Hi ,

I want to register one new css file as part of GRAY_TAB theme. We are using siebel version 8.1.1.11.10.

I am trying to modify theme.js file as part of this process.

I found  a sample code for this in bookshelf.

I have figured all other parts except the part 'new_css_id'

Can you please let  me know what is this new_css_id and where to configure this?

SiebelApp.ThemeManager.addResource(

    "GRAY_TAB",

    {

       css : {

               "new_css_id" : "files/theme-gray.css"  // Location of CSS file which needs to be added as part of existing theme

             }

    }

);

*/

Thanks and Regards,