You also need to publish your first Announcement. If you have not published any Announcements, you will see a crossed out eyeball. Once you send out an Announcement, the crossed-out eyeball will go away. You can also go into the Student View to make sure that your students can see your Announcement

I recommend that you "pin" the most recent Announcement(s) to the top of your Home Page. To do this, go into your Course Settings. Then scroll down to the bottom of the page and look for the words more options in tiny blue letters. Click on that. Now, you'll have an option to "pin" the Announcements.

@chriscas @greydon  Once again, here I am explaining more options.  It gets kind of old. The option of "pinning" Announcements to the top of the Home Page should show up when a Teacher clicks on Announcements. One possible solution would be to create a Gear Icon, like the one in the Gradebook, to allow for this global setting.