Once you log in at http://omdsi.org/wp-login.php
Click +New in the toolbar and select Post
You will now be in the Post Editor
In the Author Category box, select whether you are entering a blog post or an announcement.
In the Featured Image box, select an image if you want something other than the OMDSI logo to be associated with the post.
Once you click Publish, the post will on the omdsi.org homepage and shared on Twitter and Facebook.