Welcome! Quick answer is to just head over to the Medium blog where they are answering questions like this: https://blog.medium.com/
Tangential answer is that your questions remind me of people who join a community I run outside of Medium. Often someone will join that community and immediately start asking how to achieve the most advanced goals. I used to just answer them in a straight forward way.
But then I started to realize that the problem wasn’t a lack of information, but rather that the person asking was in a rush. Paid writing on Medium, along with running Publications, are the advanced side of what happens in this community. And there’s no rush to get there. Publish something for free first. Spend a few months just reading. I guarantee you will bump into the answers to these questions you’re asking, but more importantly, you’ll learn the fundamentals of how this community works. There isn’t documentation for that — you just have to participate.