you don't me editing, but a split screen edit right? sorry..just want to be clear...
if so, simple....add 4 layers of video...one on top of each other
double-click the 1st one... in the canvas, take your mouse, move it to the corner until you find the square icon..then drag the window in to shrink it.
repeat the steps for the other windows.
you can make this far more precise after double clicking by clicking on the 'motion' tab in the viewer. you can make exact movements by typing in measurements as to where you want things to go (center and anchor pts) and by changing the scale