Using a supernatural ability is a standard action unless noted otherwise and generally does not provoke an attack of opportunity. Supernatural abilities may have a use limit or be usable at will, just like spell-like abilities. However, supernatural abilities do not provoke attacks of opportunity and never require Concentration checks.
Unless otherwise noted, a supernatural ability has an effective caster level equal to the creature's Hit Dice. The saving throw (if any) against a supernatural ability is 10 + 1/2 the creature's HD + the creature's ability modifier (usually Charisma).