You have to open the manual or the help file to obtain information on how to save a section of recording from the DVR application. I've installed BackupViewer, but it appears there is no way to access its main interface. I don't have compatible devices on my network as well to test the recording features, but here is a tip: simply connect to the DVR's interface and switch to the Playback section. Play the video file, mark it and then cut it. This works for most of the DVR and NVR devices that have cameras and recordings already stored on them.