Your first stop would be hitting user management and, if desired, create some additional users and user groups. This way you can assign the folks who logon to the box each their own network share (partition), quotas, limitations, complete access.

Of course you can also just select Network Share management and create new shares. You then assign the users or user groups to a share and you are good to go.

BTW if this all is too complex for you, one account with administrator rights will gain access to everything and anything of course. If you have setup everything (the shares shown above are defaults as installed by the QNAP installation) you can access your shares. Either you do it though FTP login, web based .. or just plain old silly Windows Networking:

Here we can see the network shares we just made. For each share you could assign a drive letter and bind it into your operating system. Easy stuff you are used to I guess.

Let's move towards device configuration from the menu. This section is just delicious. Now you could use each HDD that you add into the QNAP TS-439 just as a single disk volume, with each disk shared. But built into the device is an actual RAID controller.

Here you can configure your drives in RAID 0/1/5/6/5+spare configurations. There's online RAID Capacity Expansion and Online RAID Level Migration as well. So this is done on the fly.

If you are not used to RAID configurations or even know what it is, just have a look at the screenshot and see how well it's explained. Just push the buttons and the device will do the rest for you. We ended up striping two drives (RAID 0) and made one big partition.

If you go for redundancy and speed, I'd recommend RAID 5 where you can bind 3 or 4 drives together. So that's a lot of flexibility there.  You can use the HDDs all alone in single disk volumes, stripe them, mirror them, combine RAID features heck it even supports a hot-spare.

Great stuff, yet one downside comes to mind. This is hardware RAID, should the QNAP device fail .. you lost your data. So inevitably if there is high profile data on the device, you do need to backup it on a regular basis.