You may worry about finding the right words, crying or not knowing what to say. You do not need a neatly organised account. “I don’t know where to start” is enough to begin.
The professional may ask what brought you, how daily life is affected, about your health and what you hope will change. Questions about previous support, important relationships or safety can help them understand your needs. They should explain the reason for a question when it is unclear.
It is all right to need time
You can say: “I cannot talk about that yet.” The therapist may explain if some information is needed for safe care and discuss how to proceed. They should not assume you are ready to tell everything.
A few notes may help. Ask beforehand whether medication details or previous reports are needed.
A clearer next step
The first appointment may not answer everything. You should nevertheless leave with a clearer understanding of what the professional thinks, what remains uncertain and what they suggest next.
Clarify costs, privacy and contact between sessions. You can take time to think; one appointment does not commit you to a long course of therapy.