Hi
Place clip 1 on video track 1
Place clip 2 on the overlay track so it is above clip1. Clip 2 will overlay Clip1.
Click the FX button for Clip 2 (on the overlay track)and select SCALE
Adjust horizontal scale to 0.5. Maintain the AR and the vertical scale will also be 0.5
Now add the POSITION effect.
Adjust the horizontal value to 25
The overlay clip will now cover half the frame.
Click the FX button for Clip 1 (main track)and select SCALE
Adjust horizontal scale to 0.5. Maintain the AR and vertical scale will also change to 0.5
Now add the POSITION effect.
Adjust the horizontal value to -25
Both clips will now be seen side by side. The AR will have been maintained for each so there will be bars (or chequered areas) at the top and bottom of the frame. This isinevitable as you can't get two full 16:9 frames next to each other without cropping one or both clips.
If you want the clips one above the other then enter the values into the vertical boxes.
Nat