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:
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.
Hope that helps. If not please provide a bit more context about what you are trying to achieve.