Since it has to happen before we determine if you've got enough ranks to be at your circle, it happens automatically. There were plans to allow you to specify which magic skills you wanted to be grandfathered in which order (I think the skills are 90/80/75/70% of your PM, in descending order but that's just off the top of my head), but they've fallen by the wayside and I don't know if they'll be in by the time we release.
--
"The ninety and nine are with dreams, content but the hope of the world made new, is the hundredth man who is grimly bent on making those dreams come true." -E.A.P.