I'm just trying to understand how Bin Locations in Advanced Inventory Settings works. I have MAIN WHSE as my Inventory Site and in there, I added BIN A. 

I have 5000 items, all of them have no bin location. Let's say those items are located in BIN A in the warehouse, Don't I need to assign each of them to BIN A?

or am I doing this all wrong? Thanks for any help.