After adding a network recorder to SageTV through the DVBViewer Recorder config utility, you need to add this new video source in SageTV. So let's start SageTV and go to the video source setup for adding a new video source.
If you correctly added your encoder to SageTV, you should see it in the list. To continue click on you network recorder in the list.
Then select the "Digital TV Tuner" as the input you want to use. As we are faking a digital tuner (DVB-T) this is the only choice you have.
With a real tuner you would have seen a preview, but with a network encoder there is no preview, so click on "Device Input to Use: Digital TV Tuner" to continue.
There is only one tuning option here, so select it to continue.
Select whatever option you need for populating the SageTV program guide :
US / Canada / XMLTV : this is what you should use with XMLTV guide data. Remember that the channel numbers your XMLTV plugin must import are the SageTV channel numbers you edited in the DVBViewer Recorder config utility.
Use TVTV : if you want to use TVTV. I don't know however how to map TVTV channels to the SageTV channel numbers you selected in the DVBViewer Recorder config utility.
Do Not Use Program Guide Data : Select this if you want to input all your channels by hand (typing the name and the SageTV channel number) or scan for it (DVBViewer Recorder 2.0 is needed)
Use an Existing Lineup : if you already have a lineup that describe the channel list of the DVBViewer Recorder network encoder, you can choose this option
It is not recommended to scan for channels (you did it in DVBViewer), so select "No - I will scan for channels later". However if you don't have any guide date source (like XMLTV) you can scan for channels provided you are using DVBViewer Recorder version 2.0 (or newer).
Finally select "Done with channel setup". You are ready to enjoy your new network recorder.