In order to create a new storage location in SAP, the starting point is the customization transaction SPRO, under Enterprise Structure > Definition > Materials Management > Maintain storage location
Maintain Storage Locations in SPRO
The plant is needed in order to maintain the storage locations for the given structure
Plant selection for storage location maintenance
The existing storage locations will be displayed, they can be updated there. To add a new one, select the New Entries button
New storage location entries
Enter the required storage locations, and save the changes
Entering a new storage location
A Customizing request will be required
Customizing request prompt
And the new Storage locations should now appear in the list for the selected plant