There are 3 ways you could do this.
1. when you put the clips next to each other leave some space between the clips and that will give you that black bar.
2. you could make a black solid in premiere and just lay it over the two clips that you want split screened. Then just use transform to look the way you want it to.
3. put the clips side by side and apply the crop effect to both clips and apply a crop to that side of the image for both clips.