Go to your Home page, select the “Teach” tab, and find a course that you have previously created. Select the “Course Settings” from the drop down menu located directly under the course title. At the bottom of the screen that pops up, select “More Settings.”
Paste your trailer embed code into the field there (requires full embed code, not just the URL). Save your changes and exit course settings. You will see the play button for the trailer appear over the course cover at the top of the About page when you are signed out or signed in as a member who is not enrolled in the course.