The integration with Shopify does not currently support multiple locations for inventory. There are a couple of reasons for this.
On the Shopify side, the Shopify api does not provide insight into its handling of orders when placed when multiple locations are involved, so we do not have the data we need to properly allocate items on orders to locations until they are actually shipped. Shopify has an update that is currently in development mode and not yet stable that will provide this, but the schedule for final release is in October. We have access to the pre-release api and are developing with it, so we plan to be able to support this once it is released for use by Shopify
On the RICS side, we do not have inventory by location information from RICS for you. We currently only have the aggregate inventory. Inventory by location is available from RICS, and we would need to do some reconfiguration work to have RICS push that to us, but there is currently no way for us to tell RICS which store an ordered item was filled from in Shopify.