If you want to put your videos side by side without splitting them in half, use the Picture in picture option. First, you need to add a background image – for example, a simple black background. On the Import tab, click Backgrounds, find an image you like, and click it to download. Then drag the picture to the Timeline. Alternatively, you can add a picture from your library, click Add Media Files, and select an image you want to use as a background. The picture will appear on the Timeline.
Now you need to drag the video you added before from the main Video Track to the Overlay Track, so both videos are on the Overlay Track. The background picture needs to stay on the main Video Track.