
Create a new trailer project in iMovie on Mac
iMovie includes templates you can use to create Hollywood-style movie trailers. Each template lets you customize the movie title and credits—and add your own video clips and photos to build a visually appealing story. Each template also comes with a unique musical score that matches the style of the trailer.
- In the iMovie app  on your Mac, open Projects view. on your Mac, open Projects view.
- Click Create New, then click Trailer.  - If you’re editing a project, click the Projects back button on the left side of the toolbar (shown below), and then click Create New.  - If you have more than one iMovie library open, click the Library pop-up menu and choose the library where you want the trailer to reside. - The Create window appears.  
- To preview a trailer template, move the pointer over the template and click the Play button  that appears. that appears.- The duration of the trailer and the number of cast members appear below the template. Look for a template that matches the number of people in your footage. - Note: You can’t switch templates after you begin creating your trailer. If you want to use a different template for your project, you need to start over and create a new trailer. 
- Click the template you want to use for your trailer.  
- Click Create, and then click OK. - A tabbed interface appears. You add titles and credits to your trailer in the Outline pane. You add video to your trailer in the Storyboard and Shot List panes.  - When you return to Projects view, you’re asked to enter a name for the trailer. Your changes are saved automatically as you work on your trailer.