If you're just starting out with WordPress.com, I recommend you go through our new user's guide: http://learn.wordpress.com/
In 10 quick steps, you'll learn about all the best and most useful features of WordPress.com, with lots of screenshots and videos.
You can also browse our support documentation and check out the forums - you might find the answer you're looking for.
http://support.wordpress.com
http://forums.wordpress.com