It needs to be added as a NPC automation entry.
Add some text in the ability description - something like Apply All Effects - this will be the text that you double-click on. Then, in the associated automation field (make it visible through the campaign options) add "Apply All Effects"|ApplyAllEffects (include the quotes) then tab out of the field and square brackets will be put around the Apply All Effects text in the ability description - double-click on that to trigger the automation.
Details on creature automation here: https://www.fantasygrounds.com/forum...and-Automation