Did you get it to work now ?
I am familiar with VNX block technology but new for Unified. I have installed a VNX5200 Unified with 2 DMs and 2 CS.  To start NAS, I create a standalone CIFS server. Then create Filesystems and shares but I cant find any place to create user credentials that clients should be used to connect to share folders. Please reply to my below inquiries.   I have added a screenshot from disk provisioning wizard.  As I am new to unified please straight forward replays would be helpful.
VNX5200 Unified share access