nopcommerce and retail POS

I have Prophetline point of sale, and operate a brick and mortar/web store.  My POS is designed to populate and synchronize with my shopping cart, what I wasn't told when I purchased the thing is that it's not super flexible.  Basically what I've done so far is to create a database that my pos will connect to, and nopcommerce will reside in as well.  nopcommerce has generated its tables, and prophetline has generated its related tables.  I need to figure out a way to make the data from prophetline actually appear, and function in my shopping cart, this doesn't seem like it should be that big of a deal, but being a complete newbie to owning my own business, and a super dummy when it comes to setting up web apps I need some help.  What do I need to do, or have done to make this work?

Hi, Personally, I would not approach the problem in the way you have done it.
It is probably easier, but to integrate two distinctly different systems in this way is going to make it virtually impossible to upgrade either providers service packs etc.

You might consider writing a set of web services that simply call the NopCommerce business components, or if you do not want to reverse engineer these and figure out how they work so you can wrap them, why not just write a few simple calls directly to the database stored procedures.
Your other app would then be able to be isolated and simply call these services for both read and write operations.
You might consider using triggers on your other system to initiate a synchronisation call to NopCommerce.

It might seem like a bit more work to isolate the separate systems, but I am sure you will benefit from the ease of maintenance in the future.