mkennedy,

Simply place your jpeg on a lower (higher number) track so it will appear in front of the video clip above it. Then select it and use 'Effects' >> 'Movement effects' >> 'Size and position' to scale it and place it where you want.

You might also consider doing a fade in or out by dragging the little 5-sided icons at the top corners of the object on the timeline. To vary the playing time of a still image drag out the end.

Regards,

Carl