Hi.
If you mean your videos to appear in the Video section at SPPB Media Manager, then this is possible only if you upload the videos via SPPB Media Manager. Even if you upload your videos into the same folder via SFTP, they will not be visible in the Video section. Since the prewiev thumbnail will not be created for display.
Therefore, just create your own folder in the images directory and upload the videos there. Then you can choose them by pressing the Browse Folders button in SPPB Media Manager