When and how do I change my secondary proffession?

Was wondering how and when I can change my secondary profession?

Can you be more specific with which campaign you're playing? :s

Prophecies: you need to be ascended (beat your doppleganger) and do the profession specific quest that can be found inone of hte desert towns.

factions: Upon reaching Senji's Corner, you can pay 500g to "unlock" one secondary profession for your character. once you do, you'll be able to switch back and forth between your original secondary and any that you've unlocked for that character.

Nightfall: Once you've gotten the command post set up you can pay for secondaries just like in factions.

dont worry about it. just follow the story line. its pretty early in all 3 and you shouldn't be using your secondary to much until you are farther in the game anyways.