You can use the Chroma Key Color transition to achieve this. The Chroma Key Color transition enables you to make certain area of an image transparent.

To add solid black bars on the top and the bottom of the video, create an image with the same width and height as your video. Color the top and bottom part of the image black and rest of the image with any other color (say Blue). You can easily create such an image in Microsoft Paint.

After creating the image, add your video to the Video 1 track. Add the image to the Video 2 track. Add the Chroma Key Color transition to the transition track and select the color you want to make transparent (Blue in our case).