Step 1: Click on the + sign in the media track.
Step 2: Click VIDEOS if it isn't selected.
Step 3: Type in a keyword to search for videos.
Step 4: Click SEARCH.
Step 5: Hover over videos with your mouse to preview them.
Step 6: Click on the video to select it.
Step 7: Edit the length of the clip here.
Step 8: Click UPLOAD VIDEO to add the video to the timeline.
For more info on editing your added video clips check out : How To Edit Added Video Clips