Place one copy of your clip on the main video track, or you can put and image in the main video track for a background. Add 4 more overlay tracks. (the manual tells how to do this). Now place a copy of your video clip in each one of the overlay tracks. Then drag them (on the preview window) one to each corner. Resize them so they fit by dragging on a corner of the picture. There should be yellow handles. Viola...PIP x 4
If you don't have the Plus version then you have to do several intermediate renders to achieve this.