Stores
In LS Express, one default store is automatically created when you go through the Assisted Setup for LS Express. To view the stores' settings go to Administration > Navigate > Stores.
This will take you to the Store List, where you can open up the Store Card to configure that store's details and change things like the default customer, address, Security Filters, etc.
Multiple Stores
For each new store, you need to create a new default customer and assign a Location Code to the default customer. All items sold from that store will be deducted from the store location on that default customer.