Where to start development

Hi There,

I am new to NopCommerce.
The main purpose of coming to nop commerce is to find out how CMS systems are built in ASP.Net MVC.

Can someone please guide me from development point from where should I start if I want to alter this CMS as per the client needs.
Right now i have no idea about its development. I wonder if there is any documentation/videos available that can help me in modifying this CMS. I need to add my own modules say integrate in with external services, modify cart, add more fields, modify database, add another level of user view etc.


Thanks,
Arir Sarwar

Start with the documentation.  But note that nopCommerce is not a CMS.  It's an eCommerce platform (shopping cart, etc.).