Start with the "practice" articles that Wikipedia suggests when you begin as an editor. They might be stub articles, or articles with obvious issues, that you are expected to research and improve a little. Then edit articles where you have more domain expertise than the original authors.
They have strict rules, but I’ve had no issues editing articles after my first error. It’s certainly not like posting an answer on Stack Overflow, where you will be downvoted and flamed for a correct-but-suboptimal answer.
Most of the time when I try to edit anything, I get a message telling me I am blocked. I am never blocked because of anything I have done but because my shared IP is. It is not something "anyone can edit" as they claim.
I do not wish to have a named account, because I had to leave one after an admin started stalking me on it. I never wanted my Wikipedia editing to be about me, but about the content.