Start with easy stuff. Tell the therapist you're not ready for the hard stuff yet, you need some time to build up to it. She'll understand. Take your time feeling comfortable with the therapist. the hard stuff will come once you feel comfortable in talking with her. You could start with just talking about what's going on right now with you, maybe why your doctor referred you to a T.

Therapists are used to helping people feel comfortable enough to talk about very difficult things. She should be willing to take as much time as you need to delve in to past issues...if that's what you want! If you don't feel that's where you want to go right now, tell your T that. If what you want right now is just coping skills, say so, and your T can probably help you with that.

I know it's very hard to do, but I've found that I get the most out of therapy if I'm just honest with my T and communicate to her what I'm thinking and feeling right then. If I'm terrified to approach a subject, I'll tell her that and she'll help me to work through that terror. If I really can't talk about something right then, I tell T that and we will put it aside for a bit. As much as we'd like them to be, therapists are not mind readers...they do a good job at making us think they are, but they really aren't.