Create Local storage

As long as "SMB" is enabled in settings (it is by default), your NAS is available just like any other server.  I personally believe that Netgear is doing it's purchasers a disservice (and possibly limiting purchases) by over-emphasizing ReadyCloud.  It is completely unnecessary in many (dare I say most?) situations.

The first thing you will want to do is reserve an IP adddress for the NAS on your router. Then either use the address your router shows and go to https://ip.of.nas/admin (where ip.of.nas is the real IP) or use RAIDar to locate it and go to the setup page. If there is some reason you cannot reserve an IP on your router, you can use RAIDar to find the NAS and go to it and set a fixed IP address.  But reservation in the router is preferred (mostly in case you end up changing out a router).

From there, you can set up local users and groups.  Note that a local user is not (and cannot be) the same as a ReadyCloud user.

Once you have all the user and group accounts set as you want, your users can map the NAS as a Windows drive using the IP or name of the NAS.

Note that all of this is independent of RAID configuration.  I hope you know what you are doing not using it.  It is always important to have a backup of the NAS contents, but it is even more important that it be up to date when not using RAID.