Post to selected pages

I read somewhere that we can select or designate different pages for posts, instead of all posts going to one page but I couldn’t find how. Can someone direct me to a way to tell WP which page to put a post on? We will have 50 plus categories, 30 plus authors, 5 subdomains, and I need to have at least 3-5 different pages oneach subdomain that I can send the posts to separately.