Hi,
you need an IPTV provider. Usually the provider also offers a settop box which is used to watch IPTV. With the IPTV software you can use your DNS to records IPTV streamings on your DNS 325. Once you have recorded something, the software can be used to stream the recording to a PC or a TV which is capable of DLNA.
The installation is fairly easy. The software has to be copied to an usb stick an to the harddisk of the DNS. It uses fun_plug. The installation will be done automatically upon the next reboot.
Best regards
pitjupp