WeSupply is integrated with Magento's MSI functionality, which allows it to mark Store Locations as Warehouses from where products can be sent out. This, in turn, works with WeSupply's Disposition feature whereby products can be returned back to specific Warehouses via the WeSupply Returns functionality.
A. Setting up locations as Sources in Magento 2
Setting up your Magento instance to use multiple Sources (warehouses) can be done by exploring Magento's Inventory Management Documentation. Once your additional Source (warehouse) is set up, it'll have a Source Code that can be used in WeSupply to mark it as a warehouse for use with Dispositions. You can find your Sources in Admin -> Stores -> Inventory -> Sources and the Source Code in the Code column:
Once you have more than one Source (warehouse) configured in Magento and have your products assigned to it, upon creating a Shipment for an order, you'll be able to select which location you'd like to send the Shipment from. In the example below, we'll have two separate locations, we'll be selecting one of those to ship our item from:
B. Marking a location as a Warehouse in WeSupply
To mark your Source as a Warehouse in WeSupply, download your Stores CSV file from under the Dashboard -> Settings -> Stores section and open it up in an Editor. If the Source you've configured is a new location, add it to the list of Stores using the same format. In the CLIENTKEY column, instead of a number, add the Source Code from the Magento Admin -> Stores -> Inventory -> Sources section. After saving the CSV and uploading it into WeSupply, the location will be marked as a Warehouse in WeSupply.
You can now continue the Disposition Setup on the WeSupply-side, check out this article: How To Configure And Test Return Dispositions in WeSupply?