I have just installed knoppmyth and have a few questions to further finish the usefuliness.
1. I can not get a movie dvd to play.
2. I can't seem to find out where to change to clock.
3. How can I add on sofware? Firefox browser, some other systems tools (gui type).
4. How can I setup the firefly remote?

I am just starting out with linux and know very little about using the command line so be gentle please.
Thanks

To install firefox #apt-get install firefox
You will use apt-get to install packages (software) and upgrade existing packages.
You will need to install libdvdcss (which may not be legal in your jurisdiction) to play DVDs.
You may also want to play those DVDs with xine instead of the MythDVD player. You can set this up in the configuration page for MythVideo the command would be xine -pfhq --no-splash dvd
To set your clock #ntpdate pool (dot) ntp (dot) org
Substitute (dot) with .
I dont think the firefly remote will work with Linux but I may be wrong.

I found this link to be very helpful..

http://knoppmythwiki.org/?id=HowTo

I think you might be better served by asking on the KnoppMyth forums; the creator of the distro as well as a lot of very experienced people hang out there.

I got a Knoppmyth (R5D1, now a little old at this point) set up on a P4 a few weekends ago for SDTV use, and I was pretty impressed with it. There were definitely a few rough edges and "gotchas" though, which would have been problems if I hadn't asked for help on the forums.

http://www.mysettopbox.tv/phpBB2/

You'll need to make an account before you can even read the forums, which seems slightly sketchy, but is for technical rather than exclusivity reasons. (It keeps the load on the DB server down, which apparently has caused problems in the past.) If you're running Knoppmyth, it's totally worth signing up, just to read the archives. There is a LOT of information in the forums that's not on the Wiki.

Also, for general MythTV questions, searching the mythtv-users mailing list archives is helpful and a great resource. No account needed there:

http://www.gossamer-threads.com/lists/mythtv/