2. Outline of the major topics to cover. Start by just listing topics and pull the major topics to the top. Keep the others around in case they fall under the others or suggest something that you could follow-up with at the end of the course.
3. Arrange the major topics from the most basic to more advanced. This makes the course an easier on-ramp.
4. Also consider if the first/easiest topic is basic enough. It's easy to assume that people have certain knowledge, but you would be surprised at how covering basic material, if even quickly, can be appreciated.
5. Visit each topic and break them down into sub-topics (steps), from basic to higher level, that fit under that topic. What is key to know about this topic.
6. Start adding content and illustrations to sub-topics, imagining how you would teach each. What should they know and how is it easiest/clearest for you to communicate this information?
7. Iterate over all topics because you'll find some that should be in other places.
The tool you use to get started might be the easiest and most familiar to you (text, word, ppt, etc). That said, by the time you get to step #6, you'll probably want to be in PPT.
Good luck!