ecwid is integrated through CAS. To set up ecwid, go to Configuration>Integration>ecwid
Once logged in, specify how inventory will be handled, and then accept terms and conditions. Determine if the inventory sold in the ecwid store will be taken froma store or warehouse, or if it will not have a shared pool of inventory. If not sharing inventory, set up a store and then create a register with a web license for this store.
You are taken to the follow up screen, where you select which store or warehouse to pool the inventory. To proceed, accept the terms and conditions.