To import one video file per each slide:
Your video file will now be imported into the slide you’ve specified and appear on the timeline. The beginning and the end of the video clip will match up with the slide.
If you upload multiple video files in this mode, each file will be added to the slides one by one starting from the selected slide.
The files will be imported in the alphabetical order. You can change their position by dragging the video clips on the timeline.