Not sure exactly what you want to do ?
Each Tenant can have one or more stores but they need a different email for each store
You can make a new store in yourwebsite.com/Admin/Store/List
Then edit the customer an apply the Stores role
Then assign an email to it in yourwebsite.com/Admin/StoreMapping/List
When you login in with the assigned email you are manging the store to which that email is mapped
For more detailed information you are best to contact the developer above
