Questions Message received: 'unassigned Location' when entering or saving an Inventory Adjustment

Receiving message:'One or more lines have unassigned Location and/or Lot/Serial Number' error when saving an inventory adjustment transaction 

The Adjustment is to add a quantity to a valid Location.

The QOH for the item is -0-. The purpose of the adjustment transaction is to have bring the inventory records to reflect the proper actual QOH.

Is there a means of assigning a location to be valid for a given Inventory Item?

The location was previously used to record a quantity of the same Item before it went to zero.

Where do you go to assign a location, especially when the inventory item is at QOH -0-?