There are two catches:
1) You have to have The Burning Crusade in order to copy and test these characters because they are level 70.
2) There seems to be a 3 day wait time.
Do you want to play with Patch 2.2 sporting some free epics? Go here and start the copy process. Blizzard asks that you allow the copy process to finish before logging into the Test Realm. There is a Copy Status page where you can check your progress.
This is an excellent opportunity to not only play with the new features (and bugs) in 2.2, but also to try out a class/race combo you may be considering rolling -- all tricked out in purples.
Have fun! ... in 3 days...