The short answer is: You don't! Backbar is focused on simplicity and one of the most complex and tedious processes with other inventory software is that they require you to assign items to specific locations. You then have to remember to transfer items to other locations whenever they move (which 95% of people never do, because who has time to do that during a busy service).
Instead, Backbar allows you to setup locations and sublocations, for the purpose of taking your physical inventory counts. All items in your inventory list will show in all of your locations when taking inventory (similar to how most inventory spreadsheets work). If an item is not present in a location, just skip it.
When you view your inventory session reports, items that are skipped will not show any counts for those locations where they don't exist. You can see where items were counted and the totals at each location when you took inventory, by going to Reports > Inventory tab > Session details report. This report does breakdown your counts at each location. But in between sessions, the location of inventory is not tracked, and what is important is the on-hand total, not which area it is stored.
