As simple as this writing key reads, it is where most aspiring writers like you face a great challenge. You stare at the blank paper or screen before you and ask, what exactly do I write first?
What happed is that you got caught in the loop of perfection. You start off writing like it’s the last draft. You should know as a writer that nothing good is ever written once. That’s why books of even the best writers read better than they talk in real life.
Writing is something you have to do and do again. When you carry this consciousness, you will know that it doesn’t really matter what you started with. Write what comes to you, and afterwards, edit like God, separating the wheat from the chaff.
For beginners, part of not knowing where to start is caused by inability to manage all the information available for writing. In such cases, it is advisable to work with an outline. An outline focusses your attention on one thing at a time. The disadvantage here is that your creative imagination forgets it is still safe to wander outside the boundaries of the outline.
Write. Just write everything that comes to mind. Editors, those creative janitors, have to earn their pay after all.