You will see the "Sharing" module in several places on Sharecare. This module allows you to post on your Activity Wall and the Activity Walls of those who Follow you.
In the Activity section of your profile, you can post messages that will be seen in the daily activity feed of your followers and to users viewing your profile directly.
Simply type in the available "Share Your Thoughts" field and click Share.
Note that full urls like http://www.sharecare.com will be automatically converted to active hyperlinks.