Pinning posts is a great way to organize your stream content and increase the visibility of selected posts.
To pin a post locate the post in the stream and click the post menu button in the top right corner:
This will bring up the post menu:
Click the pin icon to include the post in the list of pinned posts for that stream. Clicking it a second time will remove the post from the list of pinned posts.
NOTE: You must be the owner, Admin or Coach of the Stream in order to Pin Posts.