Use the B2B direct hosted storefront asset store view of the WebSphere Commerce Accelerator or the Consumer direct hosted storefront asset store view of the WebSphere Commerce Accelerator (as applicable) to set up shared marketing campaigns to be used by merchants in the hosted stores.
As the hosting provider, you have the option of either setting up shared campaigns so that they always appear on the merchant hosted storefronts (for example, if you want to advertise your hosting services through your merchants) or creating typical campaigns that the merchants could adopt at their discretion.