How and when can i advance my character's classes?

[aznxknight]

Been playing for only a few days and I came across the branching classes in the powers section but have no idea how to get them. I can't find the rules in the game to explain them either.

Can someone tell me how to do all this?

 

Thanks!

[nsr]

Once you complete AD3, you will be able to choose a role for your character.