Step 1: Inside your course, look for the "Announcements" forum that is automatically generated when you create a new course.
Step 2: In the "Announcements" forum, you'll find an option to create a new announcement that is labeled as "Add discussion topic”. Click on this option to start creating your announcement.
Step 3: After you provide a title and message, scroll down and click the “Advanced” option beside the “Post to Forum” and “Cancel” button.
Step 4: Scroll down and make sure to check the “Send forum post notifications with no editing-time delay”
If the "Announcement" forum in your course has been removed or deleted, you can easily recreate it from the "Add new activity or resource" and select "Forum" activity.