Make a list of everything you do no know about writing your book. Small things —how to open chapters, titles. And large things—how to plot, hot to structure, what it should be about, voice, tone. Make a list of specifics—I do not know if Joey is married. I do not know if I can include the story about Cecilia. I do not know if you are allowed to write about real people, can I use Uncle Henry? Write everything you do not know. Give yourself several sessions to do this; you will think of things you do not know at odd times. Write them all down.
Then choose one. Write it. In all likelihood, you won’t "do it right" the first time (just as you didn’t the first time you rode a bike, got on a surfboard, solved for x). Write it again. Notice what you are learning, notice how much you already know.