Setting up access to your NAS account is pretty simple. All of the information and steps can be found in OnePortal.
Before you start, make sure that Samba is installed in Linux if you are using a Linux operating system.
Then, visit OnePortal's Shared NAS page and click the (?) icon next to the share you would like to mount. Further instructions are provided there.
Only Accessible Internally
The NAS is only accessible over the private network. If you wish to store files on it remotely, you would need to setup FTP (or some other file transfer server) and map it to the mount point of the NAS on your server. You would then connect to your server to access it.