iOS sandboxes what third party apps can access. The native videos and music apps cannot be accessed by third party apps or external storage devices.
To transfer videos or music you would need to sync with itunes then copy the music or videos to the iXpand using a computer.
one thing you should note. If the videos are from iTunes then they are DRM protected. DRM protected files are not supported by the iXpand app so even if you use a computer to transfer these files they will not be able to be played in the iXpand drive app.
