I had the same problem, give them time, they should go in to it.
That said if you want to speed the process along you can try taking a piece of kirll and get the clowns to nip at it. Then move the krill into the BTA. They will follow it in and if you're lucky they will stay there. Also I've noticed that clowns generally prefer the anemone to be close to the ground then high up in the tank.
I have a huge RBTA but it was up near the top of the tank. My clowns wouldn't touch it. After a month or two of them ignoring the RBTA I got a smaller GBTA and put it near the bottom and they hosted in it immediately. This was about 2 years ago then about 3 months ago the clowns moved to the huge RBTA near the top... go figure.
Good luck
Micah
Edited by Sculpin - November 07 2011 at 2:36pm