Assuming you want to insert a picture into a picture (PIP)...
Drag the insert clip to the track above the main clip. Each higher track overlays the track below it, so your insert video will override the main clip video.
Click the insert clip, then on VIDEO EFFECTS in the menu bar. Or click the small, yellow star at the left-bottom corner of the clip.
Click the top-left ADD EFFECTS button and chose the SCALE or CROP effect.
Click and drag the dotted boxes in the preview window or move the sliders at the left to make the image smaller. The main image will be in the background.
When satisfied click APPLY.
The MOTION effect can use KEYFRAMES to plot a trajectory. Click KEYFRAMES in the menu bar to enable it. Keyframes can be applied to many effects.
Read the ? HELP files and experiment.
Latest versions of VP are available at http://www.nchsoftware.com/videopad/