Have you run cifs setup first? You need to run 'cifs setup' from CLI or you can use System Manager and run the CIFS Setup Wizard. Once that is complete you will be able to make one or more FlexVols for which you will then create CIFS shares to point to those FlexVol(s). If you have not installed System Manager, then please do that now. The web interface, known as "filerview" which used to be https://IP_name/na_admin is no longer used for storage controller administration.
Then using System Manager create a new FlexVol, choose the NAS radio button and choose the size you want. Then create a share using and use the buttons to browse to the new FlexVol. Alter the share permissions if you desire something other than everyone full control. From there you will be able to \\filer\share to get to start creating files. NTFS security is still handled by the client as normal.