First I create a video collage in Premiere Elements, choose a template and import videos in the media bin. Then I drag one of the videos onto one of the frames. However the video is not contained within the boundaries of the frame; instead it just sprawls across the whole screen.
Perhaps it should in the era of phone video, but Premiere Elements does not handle vertical shooting very well, if at all. It seems that the base assumption is that videos are watched on horizontal screens.