These links might be useful.
how permies works
how to post on permies
I'm not finding a post specifically about how to start a new
thread.
At first, I was a bit confused between category and forum. We can only start a thread in a forum, if we're viewing category, there's no option to start a new topic.
So for example,
homesteading is a category. To start a post, we choose which forum we want to use. Depending if you are useing new view or old, or a phone, or blablastuff I don't know much about, it will look different for you. For me, when I go to Homesteading, the list of forums are on the right. I could pick
Farm income and near the top of the screen there is a button saying "New Topic". Click that to start a new thread. If you don't see the "new topic" button, you are probably looking at a category.
If you would like a topic to be in more than one forum, and you don't have pie privileges, then the easiest thing to do is "report" the post asking the staff to put it in the other forum as well. If they think it belongs there, they can make it so that the same thread appears in more than one forum. This prevents duplicate threads cluttering up the site.