Customization of Retail Server Modern POS App

Hi All,

I am working on Retail Server Modern POS.

I want to customize the retail server Modern POS by extending it. Basically I am going through the following link.

http://technet.microsoft.com/en-us/library/dn741450.aspx.

But still not able to extend it properly.

If anyone is working on this and have some documents, please share...

Thanks,

Debendra