Given that you are working with a NAS, I suspect that you can mount the NAS to the computer that is acting as your design or another Dataiku host. That would make the NAS look just like the local file system.
In addition, Dataiku has a bunch of ways to connect to file systems or via typical protocols supported by many NAS boxes like FTP and SCP:
New Dataset dialog window from Dataiku DSS. With a Speech bubble pointing to "Server Filesystem, Files in folder, FTP, SFTP, SCP, HTTP and HTTPS (with cache). The speach bubble says " One of these two groups of connection type should work with your NAS"
Once you have connected successfully for a single connection using the above.
If you are going to use the same NAS on a regular basis you might want to use a Connection particularly if you are using a password protected protocol like FTP or SCP. This will make accessing data quicker and more consistant.
To do this go to the Admin menu (It, sort of looks like the all-white side of a rubic cube, on the upper right side of your screen) -> Connections -> New Connection. In this case you will get the window below. You can use this screen to setup a reusable connection. Either to a mounted file system or via SFTP or SCP.
New Connection Dialog box with File Connection and SCP/SFTP connections highlighted in Yellow.
Hope that helps. If not please provide a bit more context about what you are trying to achieve.