iMovie for Mac: Create a new movie
To create a movie, you first create a movie project.
Important: iMovie saves automatically as you work on a movie project; you don’t have to save as you go.
Create a new movie
In Projects view, click Create New, then click Movie.
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 movie to reside.
The resolution and frame rate of your movie project are determined by the first clip you add to the timeline. iMovie now supports 4K video and frame rates higher than 30 frames per second (fps). If you want your project to be set to 4K resolution, the first clip you add to the timeline must be a 4K clip. If you want your project to be set to 60 fps, the first clip you add to the timeline must be a 60 fps clip.