Pages are static and sit outside of the blog structure and you cannot put posts on "pages." All posts will show on the main blog page. There is no way to exclude posts from the main posts (blog) page.
At wordpress.com, you organize posts by categorizing them and then you can either put the categories widget into the sidebar, or you can create a custom menu and put the categories into the custom menu.
If you do not want all the posts to show on the main page, then you can create a static front page for your site. If you wish, you can also create a "blog" page, but you do not have to if you do not want to.
