Hey Claudio,
BC is actually fairly logical in much of its design. If you think BC is difficult at all, do a bit of reading on setting up the other D365 ERP called Finance & Ops! (you will then look at BC in a whole new light!)
But, to Steven's point, if you think through the logic its actually pretty straightforward. Just in a "backwards" way. What I mean by that is to follow the logic from "I need to have an item in order to sell it". Makes sense, right? So, if you need an item, then you also need locations for the item. And accurate (hopefully!) quantities of said item in said location. In a/the warehouse.
Then if you have the item and it's quantity, in the location, in the warehouse, and you want the visibility of "picks and puts", then logically, to sell said item on an SO, you need to pick it from the quantity in the location in the warehouse and then have it assigned to a shipment because the item needs to go from you to the customer. Actually reasonably logical, right?
Once you have that linkage established, then the SO line can be processed. And from the SO flows the invoice and then the payment and the postings and such to the subledgers and ultimately the GL.
