How to Add Clips to Your iMovie Project
Select the clip.
To select an entire clip, right-click the clip’s thumbnail and choose Select Entire Clip from the menu that appears.
To select a portion of a clip, drag your mouse cursor across the thumbnail. A yellow frame appears around your selection. To change the length of the selected video, drag the handles that appear on either side. If you make a mistake while selecting video, just click any empty space within the Event pane to remove the selection frame and try again.