By default, OrderMetrics does not know which ad account goes with what store. However we have a feature through which you can create “pairs” of ad accounts and their corresponding storefronts. This is called “Presets”.
A preset is a filtered view, with your choice of products, stores, ad accounts/campaigns/ad sets, and date range. You'd start with filtering your ad spend by using the Filter Ad Spend button.
You can then filter the storefronts, products and date range:
Once you're happy with what you see, you can click on Manage Presets and save this view.