Hi chrisbeck ,
If you want to see the statistic of external sites in the ATUM Dashboard, this is not possible, unless you use custom development but as we don't offer this service you will need to hire a developer.
If what you want to do is to import the stock of the suppliers in your Woocommerce and tracking them with ATUM, you can use our premium add-on ATUM Export Pro.
I leave you here the documentation of the add-on wherre you will find useful info about how it works: https://forum.stockmanagementlabs.com/t/atum-export-pro-documentation
And I recommend you to try the demo site for free: https://stockmanagementlabs.com/addons/atum-export-pro/