hmmm, I thought I replied to this message already, but I don't see any response.
you probably figured it out, but if you didn't or anyone else is reading this, Champion Level experience is gained ANYWHERE by doing ANYTHING that gets normal experience.
For just killing any mob, you get 1 CLxp per 2 million xp, so if you kill a high level mob and get 100 million xp, you would get 50 CLxp.
Now, doing quests (specifically the Champion Level quests) or Task Dungeons will also give CLxp.
I think it was written somewhere that the order of gaining CLxp is as follows:
1) Doing Champion Level quests
2) Realm v Realm..goes very fast if you are making solid realm points
3) Task Dungeons
4) Normal quests (I may have got this reversed from #3)
5) PvE..just killing mobs
but any can and will get you to CL10 eventually.