Awesome news and as Kathy says, relax. The process will be what it is in the end, but this is a great step that will help you set some good goals for your beginnings. Likely, your first session will be focused on your introduction and time for your therapist to settle their first impressions. Remember, they are there for you so it is good to remember that ultimately, you are in control of your journey and they are a great asset.
I know that sometimes the beginning of our transition feels like a race to get things rolling along. One day, you will awaken to realize that you have set your groundwork and you are progressing and your are essentially a teen. Keep in mind that these first steps will only be walked once, enjoy them for their uniqueness in your life!