I believe this may be the blog in question http://mamamars.wordpress.com/ If so then it's wearing the Greenery theme and it does not provide for a tagline. If you do want one you will have to switch themes.
Will you please consider linking your username to your blog? Dashboard -> Users -> Personal Settings -> then scroll down to Account Details. Then scroll down to where it says ‘Website‘ select the URL for your primary wordpress.com blog and then save changes.
Now every time you sign into the forum we can all click on your username and your blog will be linked to it. And every time you leave a comment on a blog your username can be likewise clicked and your blog can be instantly located.