Well, it isn't that easy of course. However, trauma therapy is different from what you might think it is. The therapist brings you back in time via something that could probably be called a type of hypnosis, making you feel the exact same feelings from back then again and again and again. And by facing this over and over again, you can get over it. Basically you're put in the exact same position from back then. You have to relive that part of your life and relive all those emotions. And yes, that's extremely hard. Some friend of mine had to endure this... Where I only knew him as a cheerful person, by the time I drove him back home from that session, he was completely broken.
However.... everytime you go back to the past this way it will become easier. You're forced to deal with it. And that will allow your mental wounds to heal.
As for how to open up... well... psychologists are taught how to get along with people, how to be trustful. That's necessary in their job after all. And they won't tell anyone about it. If you can't find a connection to the person, you can just go to somebody else. They won't get angry at you for that. For some people it works with Therapist A, and some people rather need Therapist B. That's life. And then just answer questions. If you don't want to answer a question you can just leave it out. If you don't know the answer to a question, just let him/her rephrase that.