As with any speaker, you have to play music through it. I'd advise just letting it break in on its own as you listen to music. One thing about speakers is that they do have moving parts, and playing them does slowly degrade the drivers. It makes me a little depressed playing music through a speaker when no one is going to appreciate it.
But if you must... Just hook it via low level inputs to a tuner or CD player, set the xover at the highest point on the REL, but set the volume on low so it does not wake you up. Let it play every night when asleep for a week or so, and it should be broken in.
I'd just let it break in the old fashioned way :-)
KF