If the warehouse module has been activated you can access Locations from the menu options Inventory > Deliveries > Locations section.

Here you can view the list of your Locations and create new ones.

A cost price markup can also be applied, should you be charged storage etc.

The location can be then associated with the product when you create your sales invoice and book your stock. It's also possible to create Inventory Relocations should you need to move stock from one location to another or rectify stock movements between locations. To create a stock relocation this menu option can be found via Inventory > Inventory books > Inventory relocation.