If you have your Home Page set to Course Activity Stream, students will always see your Announcements right when they log in. However, if you want to use a Home Page other than Course Activity Stream, such as Syllabus, Modules, or a specific Page, you can change your course settings to allow Recent Announcements to display on that Home Page.
Click on Settings [1] at the bottom of your Course Navigation Menu. It should open on the Course Details [2] tab.
In the Course Details tab, scroll to the bottom and click More Options [3].
Check the box next to Show recent announcements on Course home page [4]. You can also set the number of announcements you want to show on the homepage here.
Click Update Course Details [5].
Your most recent announcements will now show at the top of the Home Page.