It will probably be in your next S/W download. Many of us that got it on the 722k's turned it off asap. It is not a very good version of a compression/ limiter and has some bad side effects. To me it makes the volume pump like a bike pump. In & out so I don't like it.
Try menu 6 then 7. Tht is if it's menus are the same as the 722k. If that isn't it then it will be menu System Setup then Audio Output. Id you have gotten the update then it should already be enabled. Even if they starte rolling it out this week it could be a few days before all 612's get it.