Barrel Rackhouse Assignments are dependent on your Rackhouse configuration. For more information on configuring your Rackhouse(s), or if you're not sure what Zones, Tiers and Rows are used for, see this resource: Rackhouse Setup (Read Time: 4 mins)
Navigate to: Barrels > Rackhouse Inventory > Onsite Barrels and select the barrels you'd like to assign to new slots:
You may also use the "Filter" function to look up barrels by name/ID:

Either way, once your desired barrels are selected, click the "Selection Actions" box and choose "Rackhouse Assignments":
Once on the Rackhouse Assignments page, specify the Rackhouse and Zone that the barrels will be assigned to, and then specify the Row & Tier. If you don't care about tracking barrel Position within the Row & Tier, leave Position as "NA". Otherwise, choose a starting Position. Select the barrels that will be assigned to this tier and then click "Assign Selected Barrels" and the system will slot the barrels into the indicated Row & Tier, and if a position was chosen, it will automatically assign them sequentially:
After clicking "Assign Selected Barrels", you'll notice that the barrel location attributes get updated, and the "Update" checkbox on the far right is checked:
In this case, the default Zone in my "Big Blue" Rackhouse was configured with 100 rows of 20 tiers each and a total storage capacity of 10,000. This implies that each tier holds 5 barrels. Consequently, the system only assigned sequential positions to the first 5 barrels. The last 5 barrels were not automatically assigned a position, because they don't fit on the tier. They are assigned to Row 1, Tier 1, but have a "0" or "undefined" position within that row/tier.
Once you have confirmed your barrel locations, click "Submit" to store them:
Barrel assignments are sent to a job queue in the background - changes will not be visible immediately. You'll receive an email when the job is complete, typically within a few minutes.