The Announcements feature, unlike Chat, is a one-way communication tool that allows you to send messages directly to parent's devices. For two-way communication, refer to this article about using the Chat feature.
This article walks through how to make an announcement from the Teacher App; for a how-to on Announcements through the Administrator Dashboard, refer to this article.
How to make an announcement
On the Home screen of the Teacher App, click the New Post icon in the top left corner. Select "Announcement" as your post type and then click "Next".
On the Recipients screen, select the student or group you would like to send a message to. You can select to send an announcement to a single student, classroom, program, all students, staff members or a specific group of students. Once you've selected the recipients, click "Next".
Enter your message and add any photos or videos to your announcement. Select the checkmark next to "Send as email" if you would like your announcement to be sent to the recipients as an email as well. When you're happy with your announcement, click "Post" to post the announcement to its recipient's feeds and send it as an email if you selected that option.
You will now see your new announcement at the top of the feed.