How do you stretch or compress the video in iMovie from one aspect ratio to another?

In iMovie, to stretch or compress a video to a different aspect ratio, select the clip in the timeline and click on the crop icon in the viewer. Choose "Crop to Fill" to adjust the framing, or use "Fit" to maintain the original aspect ratio while displaying the entire clip. You can manually resize the clip by dragging the corners to stretch or compress it as needed. Finally, ensure to preview your changes to achieve the desired look before exporting the video.