Once the drivers are installed and appear to be working, you can configure the device in MythTV. For the most part, you should be able to treat the encoder as if it were a Hauppauge WinTV PVR-x50/500 card: Tell MythTV that it's an MPEG encoding card, not an "Analog V4L capture card." The User Manual:Detailed configuration Backend section of this wiki describes MythTV backend configuration in more detail.
One caveat: On my system, the backend reported that it couldn't detect any MPEG decoding devices. Despite this fact, entering the device name (/dev/video1 in my case) and proceeding with configuration worked.
Some systems do not provide root access to the mythtv-setup program, and as a result, you may not be able to access the device while in the Capture Card setup screen. To fix this, open a terminal and access mythtv-setup by typing sudo mythtv-setup instead, after which the device should be recognized.
In the frontend, you can tweak your Recording Profiles in the usual way.