Question about posts/pages

OK, so here’s my question. I have multiple pages (over a dozen) for different categories that I will be writing articles about. Now what I need to know is how can I make a post and change where the post is placed? For instance, just as an example:

I want to write an article in the “cars” section, how can I go to “add new post”, write the post, and get it to show up in the “cars” page. I can’t find anything when it pertains to that. I get “categories” but my “categories” don’t include my “pages”. Hope this makes sense.