Announcements are like posts in a newsfeed, received by both the students and teacher of the course.
You can post an announcement within your course by opening the "Announcements" tab within your course and clicking the "New Announcement" button on the right.
Type in your subject line, compose your message and click "Send" to send it to all participants within your course.
Where will the announcements appear?
They will appear in the Announcements menu. Click the small envelope icon next to your user name in the top right corner and select to the Announcements menu on the left. You can find the announcements sent within courses and school-wide announcements on separate tabs.