The front page of the blog by default will display your posts (not pages) http://en.support.wordpress.com/post-vs-page/ in reverse chronological order, with the most recently published post on top. If you do not want all the posts to show on the front page, then you can create a static front page called for example “Welcome” for your site and a “Blog” page for posts.
To do that create two pages > http://en.support.wordpress.com/pages/ After you do that you go to > Settings > Reading and make the designation change and click “save changes”.
You can enable and disable comments on free hosted WordPress.com blogs on this page > Settings > Discussion
Discussion settings is where you set up defaults for comments.
You can also override the default settings and enable or disable future comments on any individual post or page.
Note: By default, new blogs on WordPress.com will have the Discussion hidden. You can reveal it by clicking on Screen Options http://en.support.wordpress.com/screen-options/ on the top right corner of your Admin page, and checking the box that says Discussion so the module is included. http://en.support.wordpress.com/modules/#list-of-modules