Warehouses can be deleted via the corresponding context menu button in the warehouse overview.
Default warehouses can generally not be deleted. In this case, you first need to make another warehouse your default warehouse.
Warehouses can only be deleted if there are no more products with stock stored there. If this is the case, a corresponding error message will appear when you try to delete the warehouse. You then need to transfer all stock still located in this warehouse before you can delete it.