Let me start by asking you if I understand you correctly: you have configured one or more warehouses and you want to allocate stock to one of them?
If this is your situation, there are multiple ways to do this, each with their own timing.
The first way to achieve this is by creating orders for the goods you want to receive. Then, when the goods arrive, you go to the "Shipping > Receive" module, you search for that order, select the warehouse at which the goods arrive just below the vendor at the left top of the screen. Then at each of the lines, you select how many items were received and need to be entered into the warehouse.
Another option is to transfer goods between warehouses or from the "no warehouse" to a specific warehouse. You can do that using the "Shipping > Transfer" menu. Then, select the From and To warehouses (or don't select a warehouse to select the "no warehouse"). On the following screen, enter the amounts you want to transfer from one warehouse to another.
Hope that helps!