The WD wireless Passports can definitely be used as network drives. When setup properly, you can definitely access files (read and write) from any computer or device on the same network.
“NAS” to me means more than a simple hard drive on the network. These things definitely are “a hard drive on the network”, but don’t have the redundancy, reliability, and speed I would associate with a proper NAS box.
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The Passport Wireless drives CAN be used like a NAS. . . BUT WD support is not wrong in not recommending you using it like a NAS . . . .
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Unlike typical NAS, the passport drives are connected via WiFI, not a Ethernet cable. Therefore, the connection is slower and inherently less reliable. You won’t be happy with large file transfers.
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Unlike a typical NAS, the HDD in the passport wireless drives are not designed for 24/7/365 uptime. I forget which drives are physically in these units, but are more like the WD “Blue” drives, rather than the Server Rated WD “Red” drives that are supplied in the WD NAS Boxes.
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Unlike a typical NAS, the WD Passports Wireless are simply not built robustly enough for 24/7/365 use. They are fine for a few hours a day, a few days a week for many years. It’s just not the hardware. . also the software.
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Unlike a typical NAS, there is no RAID backup. Most NAS boxes have at LEAST two drives to produce redundancy. This device only has a single drive inside.
HAVING SAID ALL THAT. . .
You can definitely access these drives from any computer on your network. I do it all the time. . .and I swap routinely between 3 networks (these are, afterall, portable drives). You can’t do that with a NAS 
a) You can access by using windows explorer like Mike and DM100 said.
b) You can access by typing network address in Explorer address bar (e.g. \192.168.0.100 - - > or whatever your network address your router assigns) (This works best if you use a static IP address for the drive)(I forget if you need the “\”. One way gives you file access. . .the other opens the device configuration web page)
c) You can map a network drive letter to the device (I don’t recommend this because ransomware vulnerability)
Personally,
I) I have the drive configured for a static IP address. . . and access by typing the ip address into address bar. I do this all the time. . .
II) I have found that the “network” section of the Windows Explorer is sometimes slow to update. For example, if you just boot up either the computer, or the WD passport drive, it will take a few minutes for the drive to “appear”. (but I can access the files immediately if I type the address in the address bar)
III) If I am transferring more than a few hundred MB in files. . . I will plug the USB into a computer so I can get faster transfer rates.
Finally:
What’s with the hostility??? Mike27Oct and DM100 know these products and they are generally correct in their statements. I have learned a lot from reading their posts. I smell troll.
PS: On the “WiFi Network” setting page, make sure “Share Content on Network” is checked. With the box checked, any computer on the WiFi Network will see the files. If it is not checked, you have to log onto the passport’s own wifi network can see files.
