Take a breath and try to relax. your first few sessions are going to be mainly the therapist asking you questions so that the two of you can make your therapy plans - goals.

questions like -
name
address
phone number
why you are looking for therapy (this can be however short or long you want your answer to be)
a genreal idea of your problems
what you want to accomplish in therapy.

after you have a feel for the therapist and the therapist about you the harder work begins with you or your therapist bringing up a topic or problem you discuss and work on for that session based on your problems and goals.

When I start with a new therapist I spend some time through out the week and or day before the appointmnet writing down things like why I need or want to be in therapy and what I see as my problem areas and some brainstorming on ways to fix those problems. then I sometimes take that with me to my first few therapy sessions. its amazing how when just meeting a new therapist that therapist will ask me whats your phone number and I draw a complete blank because I was so worried about the harder questions. LOL