Use Pan/Crop on each event to choose the half of it you want to show. Use Track Motion on the two tracks to move one event to one side and the other event to the other side.
I sometimes use a Split Screen Media Generator or other Checkerboard Media Generator in a separate lower layer to line everything up, than simply delete that layer when done.
Other ways to do split screen are:
Add a Cookie Cutter - Track FX to the upper most video layer. Set it to Rectangle with a setting the X or Y center to 0. Then use pan an crop to position the video.
Or add a Split Media Generator (black & white) to a new track above your top video track, make that video track a child of the Split Media Generator. Add a Mask Generator FX (defaults) to the Split Media Generator layer using the default setting. Finally change the Split Media Generators layer mode to Clip.
The alignment grid should end up snapping to the middle at some point. You can turn off the grid if you don't like it. Or you can simply type in whatever numbers work into the number fields. There shouldn't be anything preventing you from getting the split exactly where you want it, right down to the precise pixel.