Can you help me deploying a GPO ?

Hi , I try to deploy a GPO using MDT 2K13 , WDS and SCM 3.0 .

I install my custom SEVEN by PxE .

I'd like to deploy a GPO with these options changed :

- Specific Wallpaper and theme 

- Pevent changing Wallpaper and theme 

So when i'm on SCM , I expand the Windows 7 node to have : Win7SP1 Bitlocker Security 1.0 , Win7SP1 Computer Security 1.0 , Win7SP1 Domain Security 1.0 , Win7SP1 Extanded DCM Checks 1.0 , Win7SP1 User Security 1.0

So , which one should I duplicate to add these settings I told above ?

Then can you explain me the way to export it and put it on my customized windows 7 ?

Thanks a lot for your incoming answers ! 

Regards .