Microsoft Storage Server 2012 R2 is a special version of Windows server sold only with hardware appliances. It is not intended or licensed to be used as a general purpose Windows machine, but allows for creating a full-featured NAS appliance. The Storage Server 2012 license is owned by the user who owns the machine, as the two go together. No CALs are required with Storage Server. Microsoft does not intend this OS to be used for general server or workstation purposes, but allows loading standard Windows backup apps, storage apps, anti-virus, and security applications onto Storage Server 2012 or Storage Server 2008 R2.

How to Install Server 2012 R2
Recover Server 2012 R2 with Download Below and Enter License code to activate license.
https://www.microsoft.com/en-us/download/details.aspx?id=41703&WT.mc_id=rss_alldownloads_all
To start the download, click the Download button, and then do one of the following:
To start the download immediately, click Open.
To copy the download to your computer for viewing at a later time, click Save.
To cancel the download, click Cancel.