This "might" help but it's a long time since set mine up.
Go into "Maintenance" in n-Serve
On the left side of the pane scroll down to "Music Repositories"
Then click on "Network Shares" if your QNAP appears in that list, select it and click on the "Use As Back-up" button on the right of the window.
If it hasn't appeared, click on "Add New" and then enter the path to your QNAP along with any user name and password that you may have to enter to access that drive.
The path will be the IP address of the QNAP NAS, in the format \\192.168****\HDX_Backup (where your own IP address is entered in place of 192.168.***** and \HDX_Backup being the destination folder on the QNAP where you want your backup to be stored.
You can use 'Qfinder' (a download from the QNAP website) to find the IP address of your QNAP, or if you know how to log into your router, it should be listed under DCHP Clients (everything which is connected to your router)
Or simply use a free app on a smart phone to search the network for the QNAP's IP address.
Once added, you can select the drive, then click on the "Use As Backup" button on the right of the window.
I think the drive/backup store folder then only appears in the "Network Stores" section of n-Serve - but it's years since I last did this, so could easily be mistaken!
