The rules regarding special actions are covered on page 11 of the Arena rulebook. Basically, unless they specifically say they're used like a spell, attack, move, or something else that includes steps on the card, their default operation is as just another action you can take, similar to guard, which does not involve any sub-steps. You do it and then it's done, so your opponent's only time to respond is either before or after it's done (it is an action and they can respond after it's done, just at no time during it to try and counter it).