Draft a new article
If you're creating a new article, it makes sense to get a rough outline together in a sandbox. That way, you can get a handle on some of the article structure, or develop a lead paragraph that contains everything you want to tackle.
You may be anxious, but don't spend too much time editing in your sandbox. Being part of Wikipedia means contributing and engaging with other Wikipedians, and sharing your knowledge with the world.
Once you have a few solid, well-sourced paragraphs and a good overview of your topic, you should go ahead and move it into Wikipedia proper.