Person on track 1; bubble on track 2. Lots of bubbles available free from the NCH clips library. Right-click in a blank area of the bin and make that choice.
Use the POSITION effect to animate the bubble. http://help.nchsoftware.com/help/en/videopad/win/effects_animating.html
At the start of the clip create a keyframe.
Advance the scrubber (red line) to the person's next position, then drag to bubble in the preview window to match. Another keyframe will automatically be created.
Repeat this throughout the action. Any keyframe (square) can be dragged. Remove a keyframe by right-clicking it. The resulting graph will resemble this... 