Any page you create using write > page is static. A static page does not update automatically and is used to post information that does not change often, such as an "about" page. Posts you write will be on the main page, which is at http://zha1.wordpress.com/ . There is no way to rename, or change the page that the posts appear on to "blog". It's coded into the theme files and we do not have access to them.
The only way that you could do what you want, is to get your own domain name, hire a web host, download and install the wordpress software from http://wordpress.org. You would then have to open up and modify (hack) a theme's html, and possibly the php files. Not something that is recommended unless you are experienced with html and php.