It's hard for someone to give you a detailed response to the most generic of questions.
I can't know to tell you how to perform step-by-step brain surgery if the question is "what place do I take sick people to?".
You asked how to change leader traits... I pointed where you do that. You simply open that XML file in wordpad and change whatever you want to change... I assume you haven't even looked in an XML file, because most of them are pretty much in simple english, and you didn't specify what about a leader you wanted to change, so I'm not giving a specific response if I don't know the specific question.