First and foremost, get rid of the negative chatter. You are not stupid, incompetent or a failure. Banish those words forever when thinking about yourself.

Approach writing systematically. What are the points I want to present? In what order should they be presented? Often it helps to start with a short statement of the topic you will be discussing. Generally ending with a short summary to conclude the writing is helpful.

There are articles online that have tips on writing. The main thing is to start. You can always fine tune and eliminate deadwood and duplication. Good luck.